NGS US Equity☆

ITEM 1A. RISK FACTORS

You should carefully consider the following risks associated with owning our common stock. Although the risks described below are the risks that we believe are material, they are not the only risks relating to our industry, our business and our common stock. Additional risks and uncertainties, including those that we have not yet identified or that we currently believe are immaterial, may also adversely affect our business, financial condition or results of operations.

Risks Associated With Our Industry

Decreased oil and natural gas prices and oil and gas industry expenditure levels adversely affect our revenue.

Our revenue is derived primarily from expenditures in the oil and natural gas industry, which, in turn, are based on budgets to explore for, develop and produce oil and natural gas. When these expenditures decline, as they have at various times during the past several years, our revenue will suffer. The industry’s willingness to explore for, develop and produce oil and natural gas depends largely upon the prevailing view of future oil and natural gas prices. Prices for oil and natural gas historically have been, and are likely to continue to be, highly volatile. Many factors affect the supply and demand for oil and natural gas and, therefore, influence oil and natural gas prices, including:

•the level of oil and natural gas production;

•the level of oil and natural gas inventories;

•domestic and worldwide demand for oil and natural gas;

•the expected cost of developing new reserves;

•the cost of producing oil and natural gas;

•the level of drilling and completions activity;

•inclement weather;

•domestic and worldwide economic activity;

•regulatory and other federal and state requirements in the United States;

•the ability of the Organization of Petroleum Exporting Countries, national oil companies and other large producers to set and maintain production levels and prices for oil;

•political conditions in or affecting oil and natural gas producing countries;

•terrorist activities in the United States and elsewhere;

•the cost of developing alternative energy sources;

•environmental regulation; and

•tax policies.

Our rental contracts are generally short-term, and oil and natural gas companies tend to respond quickly to upward or downward changes in prices. Any prolonged reduction in drilling and production activities historically has reduced our compressor sales and materially eroded both rental pricing and utilization rates for our equipment and services and adversely affects our financial results. As a result of any such prolonged reductions, we may suffer losses, be unable to make necessary capital expenditures and be unable to meet our financial obligations.

The intense competition in our industry could result in reduced profitability and loss of market share for us.

We compete with the oil and natural gas industry’s largest equipment and service providers who have greater name recognition than we do. These companies also have substantially greater financial resources, larger operations and greater budgets for marketing, research and development than we do. They may be better able to compete because of their broader geographic dispersion and ability to take advantage of international opportunities, the greater number of compressors in their fleet or their product and service diversity. As a result, we could lose customers and market share to those competitors. These companies may also be better positioned than us to successfully endure downturns in the oil and natural gas industry.

Our operations may be adversely affected if our current competitors or new market entrants introduce new products or services with better prices, features, performance or other competitive characteristics than our products and

11

services. Competitive pressures or other factors also may result in significant price competition that could harm our revenue and our business. Additionally, we may face competition in our efforts to acquire other businesses.

The outbreak of COVID-19 and recent oil market developments could adversely impact our financial condition and results of operations.

On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus known as COVID-19 due to the risks it imposes on the international community as the virus spreads globally. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. During this time, the market began to experience a decline in oil prices in response to oil demand concerns due to the global economic impacts of COVID-19. These developments led to significant weakness in oil prices and ensuing reductions of E&P company capital and operating budgets. While economic and industry conditions have improved, further or increased outbreaks of COVID-19 could impact our financial condition and results of operations in 2022 and perhaps beyond, as further discussed in risk factors below.

In addition, the continued spread of the virus into our workforce could prevent us meeting the demands of our customers and adequately servicing existing compressors. Similarly, if our customers or suppliers experience adverse business consequences due to COVID-19, demand for our equipment and services could also be adversely affected. The magnitude and duration of potential social, economic and labor instability as a direct result of COVID-19 cannot be estimated at this time. Should any of these potential impacts continue for an extended period of time, the impact on our business could have an adverse effect on our financial position and results of operations.

Adverse macroeconomic and business conditions may significantly and negatively affect our results of operations.

As a result of the COVID-19 outbreak discussed above and other economic conditions in the United States and abroad, our revenue and profitability has been and will likely continue to be adversely affected. The condition of domestic and global financial markets and the potential for disruption and illiquidity in the credit markets could have an adverse effect on our operating results and financial condition, and if sustained for an extended period, such adverse effects could also become significant. Uncertainty and turmoil in the credit markets may negatively impact the ability of our customers to finance purchases of our products and services and could result in a decrease in, or cancellation of, orders included in our backlog or adversely affect the collectability of our receivables. If the availability of credit to our customers is reduced, they may reduce their drilling and production expenditures, thereby decreasing demand for our products and services, which could have a negative impact on our financial condition. A prolonged period of depressed prices for oil and natural gas would likely result in delays or cancellation of projects by our customers, reducing the demand for our products and services.

Additionally, if we are not able to pass along increases to our costs due to inflation on parts, fluids, labor and other aspects of our business, it may adversely affect our results of operations and cash flows.

A reduction in demand for oil could adversely affect our business.

Our results of operations depend upon the level of activity in the energy market, including oil development, production, and transportation. Oil and natural gas prices and the level of drilling and exploration activity can be volatile. As a result, the demand for our natural gas compression services will be adversely affected. A reduction in demand has, and could continue to, force us to reduce our pricing substantially. Additionally, our customers’ production from oil-weighted reserves constitutes the majority percentage of our business. These unconventional sources are generally less economically feasible to be developed in low oil price environments. A decline in demand for oil and natural gas generally has an adverse effect on our business, financial condition and results of operations.

Our industry is highly cyclical, and our results of operations may be volatile.

Our industry is highly cyclical, with periods of high demand and high pricing followed by periods of low demand and low pricing. Periods of low demand intensify the competition in the industry and often result in rental equipment being idle for long periods of time. We have been required to enter into lower rate rental contracts in response to market conditions and our rentals and sales revenue have decreased as a result of such conditions. Due to the short-term nature of most of our rental contracts, changes in market conditions can quickly affect our business. As a result of the cyclicality of our industry, we anticipate our results of operations will be volatile in the future.

12

Increased regulation or ban of current fracturing techniques could reduce demand for our compressors.

From time to time, for example, legislation has been proposed in Congress to amend the federal Safe Drinking Water Act (“SDWA”) to require federal permitting of hydraulic fracturing and the disclosure of chemicals used in the hydraulic fracturing process. Further, the EPA completed a study finding that hydraulic fracturing could potentially harm drinking water resources under adverse circumstances such as injection directly into groundwater or into production wells lacking mechanical integrity. Further, legislation to amend the SDWA to repeal the exemption for hydraulic fracturing (except when diesel fuels are used) from the definition of “underground injection” and require federal permitting and regulatory control of hydraulic fracturing, as well as legislative proposals to require disclosure of the chemical constituents of the fluids used in the fracturing process, have been proposed in recent sessions of Congress. Several states and local jurisdictions also have adopted or are considering adopting regulations that could restrict or prohibit hydraulic fracturing in certain circumstances, impose more stringent operating standards and/or require the disclosure of the composition of hydraulic fracturing fluids. While we do not perform hydraulic fracturing, many of our customers do and their activity level drives demand for our products.

More recently, federal and state governments have begun investigating whether the disposal of produced water into underground injection wells has caused increased seismic activity in certain areas. The results of these studies could lead federal and state governments and agencies to develop and implement additional regulations.

A ban of hydraulic fracturing would likely halt some projects, including unconventional projects, at least temporarily. Expanded regulations are likely to introduce a period of uncertainty as companies determine ways to proceed. Any curtailment could result in a reduction of demand for our compressors, potentially affecting both sales and rentals of our units.

We are subject to extensive environmental laws and regulations that could require us to take costly compliance actions that could harm our financial condition.

Our fabrication and maintenance operations are significantly affected by stringent and complex federal, state and local laws and regulations governing the discharge of substances into the environment or otherwise relating to environmental protection. In these operations, we generate and manage hazardous wastes such as solvents, thinner, waste paint, waste oil, wash down wastes, and sandblast material. We attempt to use generally accepted operating and disposal practices and, with respect to acquisitions, will attempt to identify and assess whether there is any environmental risk before completing an acquisition. Based on the nature of the industry, however, hydrocarbons or other wastes may have been disposed of or released on or under properties owned or leased by us or on or under other locations where such wastes have been taken for disposal. The waste on these properties may be subject to federal or state environmental laws that could require us to remove the wastes or remediate sites where they have been released. We could be exposed to liability for cleanup costs, natural resource and other damages as a result of our conduct or the conduct of, or conditions caused by, prior owners, lessees or other third parties. Environmental laws and regulations have changed in the past, and they are likely to change in the future. If current existing regulatory requirements or enforcement policies change, we may be required to make significant unanticipated capital and operating expenditures.

Any failure by us to comply with applicable environmental laws and regulations may result in governmental authorities taking actions against our business that could harm our operations and financial condition, including the:

•issuance of administrative, civil and criminal penalties;

•denial or revocation of permits or other authorizations;

•reduction or cessation in operations; and

•performance of site investigatory, remedial or other corrective actions.

Increasing attention to environmental, social and governance matters and future related reporting requirements may impact our business, financial results and stock price.

In recent years, increasing attention has been given to corporate activities related to environmental, social and governance (“ESG”) matters in public discourse and the investment community. A number of advocacy groups, both domestically and internationally, have campaigned for governmental and private action to promote change at public companies related to ESG matters, including through the investment and voting practices of investment advisers, public pension funds, universities and other members of the investing community. These activities include increasing attention and demands for action related to climate change and energy transition matters, such as promoting the use of substitutes to fossil fuel products

13

and encouraging the divestment of fossil fuel equities, as well as pressuring lenders and other financial services companies to limit or curtail activities with fossil fuel companies.

Members of the investment community have begun to screen companies for sustainability performance, including practices related to climate change. In addition, organizations that provide information to investors on corporate governance and related matters have developed ratings systems for evaluating companies on their approach to ESG matters. These ratings are used by some investors to inform their investment and voting decisions. Unfavorable ESG ratings may lead to increased negative investor sentiment toward us and our industry and to the diversion of investment to other industries, which could have a negative impact on our stock price and our access to and costs of capital.

Regulatory requirements related to ESG or sustainability reporting have been issued in the European Union that apply to financial market participants. In the United States, such regulations have been issued related to pension investments in California, and for the responsible investment of public funds in Illinois. Additional regulation is pending in other states. We expect regulatory requirements related to ESG matters to continue to expand globally. If we are not able to meet future sustainability reporting requirements of regulators or current and future expectations of investors, customers or other stakeholders, our business and ability to raise capital may be adversely affected.

Increasing attention to climate change, increasing societal expectations on companies to address climate change, and potential consumer use of substitutes to energy commodities may result in increased costs, reduced demand for our customers’ hydrocarbon products which will likely translate to reduced demand for compression services, reduced profits, increased investigations and litigation, increased governmental regulations and negative impacts on our stock price and access to capital markets.

International, national and state governments and agencies continue to evaluate and promulgate legislation and regulations that are focused on restricting greenhouse gas (GHG) emissions. Compliance with climate action regulations applicable to our customers' operations may have significant implications that could adversely affect our business and operating results in the fossil fuel sectors, and boosting demand for technologies contributing to the climate action agenda.

In the United States, the U.S. Environmental Protection Agency (EPA) has taken steps to regulate GHG emissions as air pollutants under the U.S. Clean Air Act of 1970, as amended. The EPA's Greenhouse Gas Reporting Rule requires monitoring and reporting of GHG emissions from, among others, certain mobile and stationary GHG emission sources in the oil and natural gas industry. In addition, the U.S. government has proposed rules in the past setting GHG emissions standards for, or otherwise aimed at reducing GHG emissions from, the oil and natural gas industry. Caps or fees on carbon emissions, including in the U.S., have been and may continue to be established and the cost of such caps or fees could disproportionately affect the fossil fuel sectors. We are unable to predict whether and when the proposed changes in laws or regulations ultimately will occur or what they ultimately will require, and accordingly, we are unable to assess the potential financial or operational impact they may have on our business. Other developments focused on restricting GHG emissions include the Regional Greenhouse Gas Initiative, the Western Climate Action initiative, and various state programs implementing the California Global Warming Solutions Act of 2006 (known as Assembly Bill 32).

Requirements and voluntary initiatives to reduce greenhouse gas emissions, as well as increased climate change awareness, may result in increased costs for the oil and gas industry to curb greenhouse gas emissions and could have an adverse impact on demand for oil and natural gas.

International, national, and state governments, agencies and bodies continue to evaluate and promulgate regulations and voluntary initiatives that are focused on restricting GHG emissions. These requirements and initiatives are likely to become more stringent over time and to result in increased costs for the oil and gas industry to curb GHG emissions. In addition, these developments, and public perception relating to climate change, may curtail production and demand for hydrocarbons such as oil and natural gas by shifting demand towards and investment in relatively lower carbon energy sources such as wind, solar and alternative energy solutions. If renewable energy becomes more competitive than fossil-fuel energy globally, it could have a material effect on our results of operations.

The potential for climate related changes may pose future risks to our operations and those of our customers.

These changes can include extreme variability in weather patterns such as increased frequency and severity of significant weather events (e.g. flooding, hurricanes and tropical storms), natural hazards (e.g., increased wildfire risk), rising mean temperature and sea levels, and long-term changes in precipitation patterns (e.g. drought, desertification, or poor water quality). Such changes have the potential to affect business continuity and operating results, particularly at facilities in coastal areas or areas prone to chronic water scarcity.

14

Risks Associated With Our Company

A significant majority of our compressor rentals are for terms of six months or less which, if terminated or not renewed, would adversely impact our revenue and our ability to recover our initial equipment costs.

The length of our compressor rental agreements with our customers varies based on customer needs, equipment configurations and geographic area. In most cases, under currently prevailing rental rates, the initial rental periods are not long enough to enable us to fully recoup the average cost of acquiring or fabricating the equipment. Of the 1,254 compressors rented at December 31, 2021, 827 were rented on a month-to-month basis. Given the volatility of the oil and gas market, we cannot be sure that a substantial number of our customers will continue to renew their rental agreements or that we will be able to re-rent the equipment to new customers or that any renewals or re-rentals will be at comparable rental rates. The inability to timely renew or re-rent a substantial portion of our compressor rental fleet has and will have a material adverse effect upon our business, financial condition, results of operations and cash flows.

We could be subject to substantial liability claims that could harm our financial condition.

Our products are used in production applications where an accident or a failure of a product can cause personal injury, loss of life, damage to property, equipment or the environment, or suspension of operations. While we maintain insurance coverage, we face the following risks under our insurance coverage:

•we may not be able to continue to obtain insurance on commercially reasonable terms;

•we may be faced with types of liabilities that will not be covered by our insurance, such as damages from significant product liabilities and from environmental contamination;

•the dollar amount of any liabilities may exceed our policy limits; and

•we do not maintain coverage against the risk of interruption of our business.

Any claims made under our policies will likely cause our premiums to increase. Any future damages caused by our products or services that are not covered by insurance, are in excess of policy limits or are subject to substantial deductibles, would reduce our earnings and our cash available for operations.

A significant amount of our revenues and accounts receivable are related to one customer and a loss of this customer or other current customers could adversely affect our results of operations.

Our business is dependent not only on securing new customers but also on maintaining current customers. We had one customer that accounted for an aggregate of approximately 40% of our revenue for the year ended December 31, 2021, and the same customer accounted for an aggregate of approximately 30% of our revenue for the year ended December 31, 2020. At December 31, 2021, this same customer accounted for an aggregate of 46% of our accounts receivable. Unless we are able to retain our existing customers, or secure new customers if we lose one or more of our significant customers, our revenue and results of operations would be adversely affected. In addition, the default on payments by our significant customer or other important customers would negatively impact our cash flow and current assets.

Loss of key members of our management could adversely affect our business.

In keeping with our streamlined approach to our business, our executive management team consists of three officers: our (i) Chief Executive Officer, (ii) Chief Financial Officer and (iii) Vice President of Technical Services. We depend on the continued employment and performance of these three key members of our executive management team. In particular, we are significantly reliant upon the leadership and guidance of Stephen C. Taylor, who has been our President, Chief Executive Officer and Board member since 2004. In addition to his management duties, Mr. Taylor has been instrumental in our communications and standing with the investment community. If any of our key executives resign or become unable to continue in their present role and is not adequately replaced, our business operations could be materially adversely affected. We do not carry any key-man insurance on any of our officers or directors.

15

The erosion of the financial condition of our customers could adversely affect our business.

Many of our customers finance their exploration and development activities through cash flow from operations, the incurrence of debt or the issuance of equity. During times when the oil or natural gas markets are weak, our customers are more likely to experience a downturn in their financial condition. Many of our customers’ equity values and liquidity substantially declined during the most recent fall in oil and natural gas prices, and in some cases access to capital markets may be an unreliable source of financing for some customers. The combination of a reduction in cash flow resulting from declines in commodity prices, a reduction in borrowing bases under reserve-based credit facilities and the lack of availability of debt or equity financing may result in a reduction in our customers’ spending for our products and services in 2022. For example, our customers could seek to preserve capital by canceling month-to-month contracts, canceling or delaying scheduled maintenance of their existing natural gas compression equipment or determining not to enter into any new natural gas compression service contracts or purchase new compression equipment.

We might be unable to employ qualified technical personnel, which could hamper our present operations or increase our costs.

Many of the compressors that we sell or rent are mechanically complex and often must perform in harsh conditions. We believe that our success depends upon our ability to employ and retain a sufficient number of technical personnel who have the ability to design, utilize, enhance and maintain these compressors. Our ability to maintain and expand our operations depends in part on our ability to utilize and increase our skilled labor force. The demand for skilled workers is high, and supply is limited. A significant increase in the wages paid by competing employers could result in a reduction of our skilled labor force or cause an increase in the wage rates that we must pay or both. If either of these events were to occur, our cost structure could increase and our operations and growth potential could be impaired.

We may require a substantial amount of capital to expand our compressor rental fleet and grow our business.

During 2022, the amount we will spend on capital expenditures related to rental compression equipment will be determined primarily by the activity of our customers. The amount and timing of any capital expenditures may vary depending on a variety of factors, including the level of activity in the oil and natural gas exploration and production industry and the presence of alternative uses for our capital, including any acquisitions that we may pursue.

During the past year, we funded our capital expenditures through cash flows from operations. Although we believe that cash on hand and cash flows from our operations and/or potential bank borrowing from line of credit will provide us with sufficient cash to fund our planned capital expenditures for 2022, we cannot assure you that these sources will be sufficient. We may require additional capital to fund any significant unanticipated capital expenditures, such as a material acquisition. To the extent we would require any necessary capital, it may not be available to us when we need it or on acceptable terms. Our ability to raise additional capital will depend on the results of our operations and the status of various capital and industry markets at the time we seek such capital. Failure to generate sufficient cash flow, together with the absence of alternative sources of capital, could have a material adverse effect on our business, financial condition, results of operations or cash flow.

Our debt levels may negatively impact our current and future financial stability.

Should we utilize our full debt capacity, growth beyond that point could be impacted. As a result of our indebtedness at any given point in time, we might not have the ability to incur any substantial additional indebtedness. The level of our indebtedness could have several important effects on our future operations, including:

•our ability to obtain additional financing for working capital, acquisitions, capital expenditures and other purposes may be limited;

•a significant portion of our cash flow from operations may be dedicated to the payment of principal and interest on our debt, thereby reducing funds available for other purposes; and

•our leverage if increased to an unacceptable level, could make us more vulnerable to economic downturns.

If we borrow under our credit line and are unable to service our debt, we will likely be forced to take remedial steps that are contrary to our business plan.

We believe that our current cash position and anticipated cash flow from operations and the amount available under our line of credit will be sufficient to meet our capital needs through 2022. However, if we were to materially borrow under our line of credit or other borrowing arrangements, it is possible that our business will not generate sufficient cash flow from

16

operations to meet any debt service requirements and the payment of principal when due depending on the amount of borrowings at any given time. If this were to occur, we may be forced to:

•sell assets at disadvantageous prices;

•obtain additional financing; or

•refinance all or a portion of our indebtedness on terms that may be less favorable to us.

Our current credit agreement contains covenants that limit our operating and financial flexibility and, if breached, could expose us to severe remedial provisions.

Under the terms of our current credit agreement, we must:

•comply with various leverage, commitment coverage and other customary ratios;

•not exceed specified levels of debt

•comply with limits on asset sales;

•comply with limits on cash dividends;

•and other customary limitations.

Our ability to meet the financial ratios and tests under our credit agreement can be affected by events beyond our control, and we may not be able to satisfy those ratios and tests. A breach of any one of these covenants or requirements could permit the lending organization to accelerate outstanding amounts so that it is immediately due and payable. If a breach occurs, no further borrowings would be available under our credit arrangement. If we are unable to repay any outstanding amounts, the lending organization could proceed against and foreclose on the assets we pledged as collateral to secure payment of our indebtedness.

If we fail to acquire or successfully integrate additional businesses, our growth may be limited and our results of operations may suffer.

As part of our business strategy, we evaluate potential acquisitions of other businesses or assets. However, there can be no assurance that we will be successful in consummating any such acquisitions. Successful acquisition of businesses or assets will depend on various factors, including, but not limited to, our ability to obtain financing and the competitive environment for acquisitions. In addition, we may not be able to successfully integrate any businesses or assets that we acquire in the future. The integration of acquired businesses is likely to be complex and time consuming and place a significant strain on management and may disrupt our business. We also may be adversely impacted by any unknown liabilities of acquired businesses, including environmental liabilities. We may encounter substantial difficulties, costs and delays involved in integrating common accounting, information and communication systems, operating procedures, internal controls and human resources practices, including incompatibility of business cultures and the loss of key employees and customers. These difficulties may reduce our ability to gain customers or retain existing customers, and may increase operating expenses, resulting in reduced revenues and income and a failure to realize the anticipated benefits of acquisitions.

Failure to effectively manage our business and growth could adversely affect our operating results and our internal controls.

Our strategy envisions the expansion and growth of our business, subject to the demand for oil and gas and the impact of the other risks set forth in this risk factor section and elsewhere in this Report. Growth may place a strain on our management systems and resources. We must continue to refine and expand our business capabilities, our systems and processes, and our access to financing sources. If we expand, we must continue to hire, train, supervise and manage new employees. We cannot assure that we will be able to:

•meet our capital needs;

•upgrade and expand our office and manufacturing infrastructure so that it is appropriate for our level of activity;

•expand our systems effectively or efficiently or in a timely manner, including financial and management controls, reporting systems and procedures; and

•attract, hire, train and retain additional highly skilled and motivated officers and employees and allocate our human resources optimally.

17

If we are unable to manage our growth, our financial conditions and results of operations may be adversely affected.

Liability to customers under warranties and indemnification provisions may materially and adversely affect our results of operations.

We provide warranties as to the proper operation and conformance to specifications of the equipment we manufacture. Our equipment is complex and often deployed in harsh environments. Failure of this equipment to operate properly or to meet specifications may increase our costs by requiring additional engineering resources and services, replacement of parts and equipment or monetary reimbursement to a customer. We have in the past received warranty claims and we expect to continue to receive them in the future. To the extent that we incur substantial warranty claims in any period, our reputation, our ability to obtain future business and our results of operations could be materially and adversely affected.

Our rental and sales contracts provide for varying forms of indemnification from our customers and in most cases may require us to indemnify our customers. Under some of our rental and sales contracts, liability with respect to personnel and property is customarily assigned on a “knock-for-knock” basis, which means that we and our customers assume liability for our respective personnel and property. However, in certain rental and sales contracts we assume liability for damage to our customer’s property and other third-party on the site resulting from our negligence. Since our products are used in production applications in the energy industry, expenses and liabilities in connection with accidents involving our products and services could be extensive and may exceed our insurance coverages.

Our income taxes may change.

We are subject to income tax on a jurisdictional or legal entity basis and significant judgment is required in certain instances to allocate our taxable income to a jurisdiction and to determine the related income tax expense and benefits. Losses in one jurisdiction generally may not be used to offset profits in other jurisdictions. As a result, changes in the mix of our earnings (or losses) between jurisdictions, among other factors, could alter our overall effective income tax rate, possibly resulting in significant tax rate increases.

We are regularly audited by various tax authorities. Income tax audit assessments or changes in tax laws, regulations, or other interpretations may result in increased tax provisions which could materially affect our operating results in the period or periods in which such determinations are made or changes occur.

Failure to maintain effective internal controls could have a material adverse effect on our operations.

Section 404 of the Sarbanes-Oxley Act requires annual management assessments of the effectiveness of our internal control over financial reporting. If we fail to maintain effective internal controls, we may not be able to ensure that we can conclude on an ongoing basis that we have effective internal controls over financial reporting in accordance with Section 404 of the Sarbanes-Oxley Act. Moreover, effective internal controls are necessary for us to produce reliable financial reports and to help prevent financial fraud. If, as a result of deficiencies in our internal controls, we cannot provide reliable financial reports or prevent fraud, our business decision process may be adversely affected, our business and operating results could be harmed, investors could lose confidence in our reported financial information, and the price of our stock could decrease as a result.

We are exposed to risks related to computer systems failures or cyber security threats

In the conduct of our business we are dependent upon our computing systems and those of third parties to collect, store, transmit and process data used in our operational activities and to record, process and track financial transactions. If interruptions were to occur we would be unable to access these systems for a period of time and there is a risk of data loss. Data backup and storage measures are in place that would allow recovery in a time frame that we believe would not materially impact our ability to conduct business.

We are also subject to cyber security attacks and have taken steps to minimize the probability of an attack penetrating our systems. These include network security, virus protection, filtering software and intrusion protection measures.

18

Risks Associated With Our Common Stock

The price of our common stock may fluctuate.

The trading price of our common stock and the price at which we may sell securities in the future are subject to substantial fluctuations in response to various factors, including our ability to successfully accomplish our business strategy, the trading volume of our stock, changes in governmental regulations, actual or anticipated variations in our quarterly or annual financial results, our involvement in litigation, general market conditions, the prices of oil and natural gas, announcements by us and our competitors, our liquidity, our ability to raise additional funds, and other events such as those discussed in the factors above.

Future sales of our common stock could adversely affect our stock price.

Substantial sales of our common stock in the public market, or the perception by the market that those sales could occur, may lower our stock price or make it difficult for us to raise additional equity capital in the future. According to filings made with the Securities and Exchange Commission in February 2022, an aggregate of approximately 27.9% of the outstanding shares of our common stock are owned by four institutional investors, each of which owns more than 5% of our outstanding shares as of the date of their respective filings in February 2022. Potential sales of large amounts of these shares in a short period of time by one or more of these significant investors could have a negative impact on our stock price. In addition, potential sales of our common stock by our directors and officers, who beneficially own approximately 6.5% of the outstanding shares of our common stock as of March 14, 2022, and because of the negative perception of sales by insiders, could also have a negative impact on our stock price.

We have a comparatively low number of shares of common stock outstanding and, therefore, our common stock may suffer from limited liquidity and its prices will likely be volatile and its value may be adversely affected.

Because of our relatively low number of outstanding shares of common stock, the trading price of our common stock will likely be subject to significant price fluctuations and limited liquidity. This may adversely affect the value of your investment. In addition, our common stock price is subject to fluctuations in response to variations in quarterly operating results, changes in management, future announcements concerning us, general trends in the industry and other events or factors such as those described above.

If we issue debt or equity securities, you may lose certain rights and be diluted.

If we raise funds in the future through the issuance of debt or equity securities, the securities issued may have rights and preferences and privileges senior to those of holders of our common stock, and the terms of the securities may impose restrictions on our operations or dilute your ownership in our Company.

We currently have on file with the SEC an effective "universal" shelf registration statement on Form S-3, which enables us to sell, from time to time, our common stock and other securities covered by the registration statement in one or more public offerings. The shelf registration statement allows us to enter the public markets and consummate sales of the registered securities in rapid fashion and with little or no notice. Issuances of securities under our shelf registration statement may dilute our existing shareholders.

If securities analysts downgrade our stock or cease coverage of us, the price of our stock could decline.

The trading market for our common stock relies in part on the research and reports that industry or financial analysts publish about us or our business. We do not control these analysts. Furthermore, there are many large, well-established, publicly traded companies active in our industry and market, which may mean that it is less likely that we will receive widespread analyst coverage. If one or more of the analysts who do cover us downgrade our stock, our stock price would likely decline rapidly. If one or more of these analysts cease coverage of our company, we could lose visibility in the market, which in turn could cause our stock price to decline.

Provisions contained in our governing documents could hinder a change in control of us.

Our articles of incorporation and bylaws contain provisions that may discourage acquisition bids and may limit the price investors are willing to pay for our common stock. Our articles of incorporation and bylaws provide that:

19

•directors are elected for three-year terms, with approximately one-third of the board of directors standing for election each year;

•cumulative voting is not allowed, which limits the ability of minority shareholders to elect any directors;

•advance notice for nominations of directors by shareholders and for shareholders to include matters to be considered at our annual meeting;

•the unanimous vote of the board of directors or the affirmative vote of the holders of not less than 80% of the votes entitled to be cast by the holders of all shares entitled to vote in the election of directors is required to change the size of the board of directors; and

•directors may be removed only for cause or by the holders of not less than 80% of the votes entitled to be cast on the matter.

Our Board of Directors has the authority to issue up to five million shares of preferred stock. The Board of Directors can fix the terms of the preferred stock without any action on the part of our shareholders. The issuance of shares of preferred stock may delay or prevent a change in control transaction. In addition, preferred stock could be used in connection with the Board of Directors’ adoption of a shareholders’ rights plan (also known as a poison pill), which would make it much more difficult to effect a change in control of our Company through acquiring or controlling blocks of stock. Also, our directors and officers as a group will continue to beneficially own stock and although this is not a majority of our stock, it confers substantial voting power in the election of directors and management of our Company. This would make it difficult for other minority shareholders to effect a change in control or otherwise extend any significant control over our management. This may adversely affect the market price and interfere with the voting and other rights of our common stock.

ITEM 1B. UNRESOLVED STAFF COMMENTS

None.

ITEM 2. PROPERTIES

The table below describes the material facilities owned or leased by Natural Gas Services Group as of December 31, 2021:

Location Status Square Feet Uses

Midland, Texas Owned 70,000 Compressor fabrication, rental and services

Lewiston, Michigan Owned 15,360 Compressor fabrication, rental and services

Midland, Texas Owned 45,000 Corporate office

Bloomfield, New Mexico Owned 7,000 Office and parts and services

Godley, Texas Leased 5,000 Parts and services

Galeton, Colorado Leased 4,800 Parts and services

Bridgeport, Texas Leased 4,500 Office and parts and services

Midland, Texas Owned 4,100 Parts and services

Vernal, Utah Leased 3,200 Parts and services

Carrollton, Ohio Leased 2,600 Parts and services

Wheeler, Texas Leased 2,160 Parts and services

We believe that our properties are generally well maintained and in good condition and adequate for our purposes.

ITEM 3. LEGAL PROCEEDINGS

From time to time, we are a party to various legal proceedings in the ordinary course of our business. While management is unable to predict the ultimate outcome of these actions, it believes that any ultimate liability arising from these actions will not have a material effect on our financial position, results of operations or cash flow. We are not currently a party

20

to any bankruptcy, receivership, reorganization, adjustment or similar proceeding, and we are not aware of any material threatened litigation.

ITEM 4. MINE SAFETY DISCLOSURES

Not applicable.

PART II

ITEM 5. MARKET FOR REGISTRANT’S COMMON EQUITY, RELATED STOCKHOLDER MATTERS AND

ISSUER PURCHASES OF EQUITY SECURITIES

Our common stock currently trades on the New York Stock Exchange under the symbol “NGS”. As of December 31, 2021 as reflected by our transfer agent records, we had 15 record holders of our common stock. This number does not include any beneficial owners for whom shares of common stock may be held in “nominee” or “street” name. On March 14, 2022, the last reported sale price of our common stock as reported by the New York Stock Exchange was $11.82 per share.

Dividends

To date, we have not declared or paid any dividends on our common stock. We currently do not anticipate paying a cash dividend on our common stock. Although we intend to retain our earnings, if any, to finance the growth of our business, our Board of Directors will have the discretion to declare and pay dividends in the future. Payment of dividends in the future will depend upon our earnings, capital requirements, and other factors, which our Board of Directors may deem relevant. Our credit agreement also contains restrictions on our paying dividends under certain circumstances.

Equity Compensation Plans

The following table summarizes certain information regarding our equity compensation plans as of December 31, 2021:

Equity compensation plans approved by security holders:

(1) Total number of shares to be issued upon exercise of options granted to employees, officers, and directors under our 1998 Stock Option Plan.

21

Sale of Unregistered Securities

We made no sales of unregistered securities during the year ended December 31, 2021. The following table summarizes our purchases of shares of common stock during the three months ended December 31, 2021.

ISSUER PURCHASES OF EQUITY SECURITIES1,2

(a) (b) (c) (d)

Common Stock

(dollars in thousands)

1 The table summarizes repurchases of (and remaining authority to repurchase) shares of our Common Stock.

2 The figures in the table reflect transactions according to the settlement dates. For purposes of our consolidated financial statements included in this Form 10-K, the impact of these repurchases is recorded according to the settlement dates.

3 On September 30, 2021, our Board of Directors authorized the repurchase of up to $10.0 million of our outstanding Common Stock in the open market (pursuant to Rule 10b5-1 plans or otherwise), block trades or privately negotiated transactions. This repurchase program is set to expire on September 30, 2022. The amounts in this column indicate the remaining amounts that may yet be expended to repurchase shares under these authorizations.

22

ITEM 6. SELECTED FINANCIAL DATA

Not applicable.

ITEM 7. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion is intended to assist you in understanding our financial position and results of operations for each of the years ended December 31, 2021 and 2020. You should read the following discussion and analysis in conjunction with our audited financial statements and the related notes.

The following discussion contains forward-looking statements. For a description of limitations inherent in forward-looking statements, see “Special Note Regarding Forward-Looking Statements” on page ii.

Overview

We fabricate, manufacture, rent and sell natural gas compressors and related equipment. Our primary focus is on the rental of natural gas compressors. Our rental contracts generally provide for initial terms of six to 60 months, with our larger horsepower units having longer initial terms. After the initial term of our rental contracts, most of our customers have continued to rent our compressors on a month-to-month basis. Rental amounts are billed monthly in advance and include maintenance of the rented compressors. As of December 31, 2021, we had 1,254 natural gas compressors totaling 297,808 horsepower rented to 83 customers, compared to 1,274 natural gas compressors totaling 287,646 horsepower rented to 80 customers at December 31, 2020. Of the 1,254 compressors rented at December 31, 2021, 827 were rented on a month-to-month basis.

We also fabricate natural gas compressors for sale to our customers, designing compressors to meet unique specifications dictated by well pressures, production characteristics and particular applications for which compression is sought. Fabrication of compressors involves our purchase of engines, compressors, coolers and other components, and our assembling of these components on skids for delivery to customer locations. These major components of our compressors are acquired through periodic purchase orders placed with third-party suppliers on an “as needed” basis, which presently requires a a minimum three to six month lead time with delivery dates scheduled to coincide with our estimated production schedules. Although we do not have formal continuing supply contracts with any major supplier, we believe we have adequate alternative sources available. In the past, we have not experienced any sudden and dramatic increases in the prices of the major components for our compressors; however, the occurrence of such an event could have a material adverse effect on the results of our operations and financial condition, particularly if we were unable to increase our rental rates and sales prices proportionate to any such component price increases.

We also manufacture a line of compressor frames, cylinders and parts, known as our CiP (Cylinder-in-Plane) product line. We use finished CiP component products in the fabrication of compressor units for sale or rental by us or sell the finished component products to other compressor fabricators. We also design, fabricate, sell, install and service flare stacks and related ignition and control devices for onshore and offshore incineration of gas compounds such as hydrogen sulfide, carbon dioxide, natural gas and liquefied petroleum gases. To provide customer support for our compressor and flare sales businesses, we stock varying levels of replacement parts at our Midland, Texas facility and at field service locations. We also provide an exchange and rebuild program for screw compressors and maintain an inventory of new and used compressors to facilitate this business.

We provide service and maintenance to our non-rental customers under written maintenance contracts or on an as-required basis in the absence of a service contract. Maintenance agreements typically have terms of six months to one year and require payment of a monthly fee.

23

The following table sets forth our revenues from each of our three operating categories for the periods presented:

Year Ended December 31,

(in thousands)

Our strategy for growth is focused on our compressor rental business. Margins, exclusive of depreciation and amortization, for our rental business historically run in the mid-40% to low-60% range, while margins for the compressor sales business tend to be in the mid-20% range. If our rental business grows and contributes a larger percentage of our total revenues, we expect our overall company-wide margins, exclusive of depreciation and amortization, to improve over time.

The oil and natural gas equipment rental and services industry is cyclical in nature. The most critical factor in assessing the outlook for the industry is the worldwide supply and demand for oil and natural gas and the corresponding changes in commodity prices. As demand and prices increase, oil and natural gas producers typically increase their capital expenditures for drilling, development and production activities, although recent equity capital constraints and demands from institutional investors to keep spending within operating cash flow have meaningfully restrained capital expenditure budgets of domestic exploration and production companies. Generally, increased capital expenditures ultimately result in greater revenues and profits for service and equipment companies.

In general, we expect our overall business activity and revenues to track the level of activity in the oil and natural gas industry, with changes in crude oil and condensate production and consumption levels and prices affecting our business more than changes in domestic natural gas production and consumption levels and prices. In recent years we have increased our rental and sales in unconventional oil shale plays, which are more dependent on crude oil prices. With this shift towards oil production the demand for overall compression services and products is driven by two general factors; an increased focus by producers on artificial lift applications, e.g., production enhancement with compression assisted gas lift; and declining reservoir pressure in maturing natural gas producing fields, especially non-conventional production. These types of applications have historically been serviced by wellhead size compressors, and continue to be, but there has also been an economic move by our customers towards centralized drilling and production facilities, which have increased the market need for larger horsepower compressor packages. We recognized this need in recent years and have shifted our cash and fabrication resources towards designing, fabricating and renting gas compressor packages that range from 400 horsepower up to 1,500 horsepower. While this is a response to market conditions and trends, it also provides us with the opportunity to compete as a full-line compression provider.

We typically experience a decline in demand during periods of low crude oil and natural gas prices. During 2019, we witnessed a moderation of crude oil prices as well as drilling and completion activity levels. During the first quarter of 2020, we saw a substantial decline in the prices for oil and natural gas. Activity levels of exploration and production companies have been and will continue to be dependent not only on commodity prices, but also on their ability to generate sufficient operational cash flow to fund their activities. Generally, though, we feel that production activities (in which we are involved) will fare better than drilling activity.

For fiscal year 2022, our forecasted capital expenditures will be directly dependent upon our customers’ compression requirements and are not anticipated to exceed our internally generated cash flows. Any required capital will be for additions to our compressor rental fleet and/or addition or replacement of service vehicles. We believe that cash on hand and cash flows from operations will be sufficient to satisfy our capital and liquidity requirements through 2022. If we require additional capital to fund any significant unanticipated expenditures, including any material acquisitions of other businesses, joint ventures or other opportunities, this additional capital could exceed our current resources, might not be available to us when we need it, or might not be on acceptable terms.

Critical Accounting Policies and Practices

We have identified the policies below as critical to our business operations and the understanding of our results of operations. In the ordinary course of business, we have made a number of estimates and assumptions relating to the reporting of results of operations and financial condition in the preparation of our financial statements in conformity with accounting

24

principles generally accepted in the United States. Actual results could differ significantly from those estimates under different assumptions and conditions. We believe that the following discussion addresses our most critical accounting policies, which are those that are most important to the portrayal of our financial condition and results of operations and require our most difficult, subjective, and complex judgments, often as a result of the need to make estimates about the effect of matters that are inherently uncertain. We describe our significant accounting policies more fully in Note 2 ("Summary of Significant Accounting Policies") to our consolidated financial statements.

Our critical accounting policies are as follows:

•revenue recognition;

•estimating the allowance for doubtful accounts receivable;

•accounting for income taxes;

•accounting for long-lived assets; and

•accounting for inventory.

Revenue Recognition Policy

The Company adopted ASC 606, Revenue from Contracts with Customers ("ASC 606") on January, 1, 2018. Revenue is measured based on a consideration specified in a customer’s contract, excluding any sale incentives and taxes collected on behalf of third parties (i.e. sales and property taxes). We recognize revenue once a performance obligation has been satisfied and control over a product or service has transferred to the customer. Shipping and handling costs incurred are accounted for as fulfillment costs and are included in cost of revenues in our Consolidated Statements of Operations.

Nature of Goods and Services

Rental Revenue. The Company generates revenue from renting compressors and flare systems to our customers. These contracts may also include a fee for servicing the compressor or flare during the rental contract. Our rental contracts typically range from six to 60 months, with our larger horsepower compressors having longer minimum contract terms. Our rental revenue is recognized over time, with equal monthly payments over the term of the contract. After the terms of the contract have expired, a customer may renew their contract or continue renting on a monthly basis thereafter.

Sales Revenue. The Company generates revenue by the sale of custom/fabricated compressors, flare systems and parts, as well as, exchange/rebuilding customer owned compressors and sale of used rental equipment. The Company designs and fabricates compressors and flares based on the customer’s specifications outlined in their contract. Though the equipment being built is customized by the customer, control under these contracts does not pass to the customer until the compressor or flare package is completed and shipped, or, in accordance with a bill and hold arrangements, the customer accepts title and assumes the risk and rewards of ownership. We request some of our customers to make progressive payments as the product is being built; these payments are recorded as a contract liability on the Deferred Income line on the consolidated balance sheet until control has been transferred. These contracts also may include an assurance warranty clause to guarantee the product is free from defects in material and workmanship for a set duration of time; this is a standard industry practice and is not considered a performance obligation.

Allowance for Doubtful Accounts Receivable

We perform ongoing credit evaluations of our customers and adjust credit limits based on management's assessment of the customer's financial condition and payment history, as well as industry conditions and general economic conditions. We continuously monitor collections and payments from our customers and maintain a provision for estimated credit losses based upon our historical experience and any specific customer collection issues that we have identified. While such credit losses have historically been within our expectations and the provisions established, we cannot guarantee that we will continue to experience the same credit loss rates that we have in the past. Management believes that its allowance for doubtful accounts is adequate; however, actual write-offs may exceed the recorded allowance.

Accounting for Income Taxes

As part of the process of preparing our financial statements, we are required to estimate our federal income taxes as well as income taxes in each of the states in which we operate. This process involves us estimating our actual current tax exposure together with assessing temporary differences resulting from differing treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities, which are included in our consolidated balance

25

sheet. We must then assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe that recovery is not probable, we must establish a valuation allowance. To the extent we establish a valuation allowance or increase this allowance in a period, we must include an expense in the tax provision in the statement of income.

Significant management judgment is required in determining our provision for income taxes, our deferred tax assets and liabilities and any valuation allowance recorded against our net deferred tax assets. We currently have no valuation allowance and fully expect to utilize all of our deferred tax assets.

ASC 740 also prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. In order to record any financial statement benefit, we are required to determine, based on technical merits of the position, whether it is more likely than not (a likelihood of more than 50 percent) that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes. If that step is satisfied, then we must measure the tax position to determine the amount of benefit to recognize in the financial statements. The tax position is measured at the largest amount of the benefit that is greater than 50 percent likely of being realized upon ultimate settlement. Our policy regarding income tax interest and penalties is to expense those items as other expense.

Long-Lived Assets

Rental Equipment, Property and Equipment (Including Retirement of Rental Equipment)

Rental equipment and property and equipment are recorded at cost less accumulated depreciation, except for work-in-progress on new rental equipment which is recorded at cost until it’s complete and added to the fleet. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Our rental equipment has an estimated useful life between 15 and 25 years, while our property and equipment has an estimate useful lives which range from 3 to 39 years. The majority of our property and equipment, including rental equipment, is a direct cost to generating revenue.

We assess the impairment of rental equipment and property and equipment whenever events or changes in circumstances indicate that the net recorded amount may not be recoverable. The following factors could trigger an impairment review: significant underperformance relative to historical or projected future cash flows; significant adverse changes in the extent or manner in which asset (or asset group) is being used or its condition, including a meaningful drop in fleet utilization over the prior four quarters; significant negative industry or company-specific trends or actions, including meaningful capital expenditure budget reductions by our major customers or other sizable exploration and production or midstream companies, as well as significant declines in oil and natural gas prices; legislative changes prohibiting us from leasing our units or flares; or poor general economic conditions. An impairment loss is recognized if the future undiscounted cash flows associated with the asset (or asset group) and the estimated fair value of the asset are less than the asset's carrying value.

Inventories

We value our total inventory (current and long-term) at the lower of the actual cost and net realizable value of the inventory. We regularly review inventory quantities on hand and record a provision for excess and obsolete inventory based primarily on current and anticipated customer demand and production requirements. The Company accesses anticipated customer demand based on current and upcoming capital expenditure budgets of its major customers as well as other significant companies in the industry, along with oil and natural gas price forecasts and other factors affecting the industry. For the year ended December 31, 2021, inventory allowance and write-off totaled $0.2 million. We ended 2021 with an inventory allowance balance of $64,000.

Our Performance Trends and Outlook

On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus known as COVID-19 due to the risks it imposes on the international community as the virus spreads globally. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. During this time, the market began to experience a decline in oil prices in response to oil demand concerns due to the global economic impacts of COVID-19. These developments led to significant weaknesses in oil prices and ensuing reductions of exploration and production company capital and operating budgets. Oil markets largely recovered in 2021, and prices have continued to rise in the early months of 2022.

With the increases in oil prices, we expect rental demand for our large and medium horsepower units to remain strong for the remainder of 2022. In terms of sales, we expect minimal compressor sales for the year due to shifts in capital

26

expenditure budget concentrations throughout the industry, including those of our major customers, as many upstream producers prefer to rent compression as opposed to purchasing units as part of their capital budget allocations. Finally, we have recently experienced and expect to continue to experience supply chain disruptions. While we believe we have a strong vendor network that provides flexibility in sourcing needed materials, we have incurred longer than normal wait times for certain components as well as increases in costs. Lastly, our relationship with our major customers continues to be strong, and they have continued to pay our invoices in a timely, consistent manner. Nevertheless, if any of these circumstances change, our business could be adversely affected.

While management anticipates that the industry and economic impact of the pandemic may have a negative effect on its results of operations in 2022 and perhaps beyond, the degree to which these factors will impact our business remains uncertain. Please read Item 1A, Risk Factors, in this report.

Results of Operations

Year Ended December 31, 2021 Compared to the Year Ended December 31, 2020

The table below shows our revenues and percentage of total revenues for each of our product lines for the years ended December 31, 2021 and 2020.

Revenue

Year Ended December 31,

(dollars in thousands)

Total revenue increased to $72.4 million from $68.1 million, or 6.4%, for the year ended December 31, 2021 compared to 2020. This increase was mainly a result of increased rental revenue (4.6% increase) primarily due to a greater number of large horsepower units being rented as well as higher sales revenue (21.7% increase) primarily due to increased parts sales partially offset by decreased compressor sales.

Rental revenue increased to $63.6 million (4.6%) from $60.8 million for the year ended December 31, 2021 compared to 2020. As of December 31, 2021, we had 2,023 natural gas compressors in our rental fleet, down from 2,224 units at year end 2020. In addition, the Company's total unit horsepower decreased by 4.7% to 418,041 at December 31, 2021 compared to 438,524 horsepower year end 2020. However, as of December 31, 2021, we had 1,254 natural gas compressors totaling 297,808 horsepower rented to 83 customers, compared to 1,274 natural gas compressors totaling 287,646 horsepower rented to 80 customers as of December 31, 2020. This increase in rented horsepower reflects the addition of 25 high horsepower compressors with 10,020 horsepower to the Company's fleet during 2021. The rental fleet had a unit utilization as of December 31, 2021 and 2020 of 62.0% and 57.3%, respectively, while our horsepower utilization for the same periods was 71.2% and 65.6%, respectively. The increase in both utilization metrics was mainly the result of the addition and increased demand for our higher horsepower units.

Sales revenue increased to $6.9 million from $5.7 million for the year ended December 31, 2021, compared to 2020. This increase in largely attributable to an increase in parts sales during 2021. Sales are subject to fluctuations in timing of industry activity related to capital projects and, as such, can vary substantially between periods.

Company management routinely reviews its inventory balances for obsolescence. Due to the slow moving nature or obsolescence of a portion of the Company's long-term inventory and inventory related to the retirement of certain rental equipment, management recorded an increase of $208,000 in the inventory allowance reserve for costs that may not be recoverable in the future. We ended 2021 with an inventory allowance balance of $64,000.

Company management routinely reviews its rental fleet to determine which units are no longer of the type, configuration, make or model that our customers are demanding or that are not cost efficient to refurbish, maintain and/or

27

operate. As a result of this review, we determined 263 units should be retired from our rental fleet. Accordingly, we recorded a $3.1 million loss on retirement of rental equipment during the year ended December 31, 2021.

Operating loss increased to $12.4 million for the year ended December 31, 2021 compared to an operating loss of $3.6 million for the year ended December 31, 2020. The increase in operating loss was mainly due to 1) an $8.1 million increase in costs of rentals primarily related to a significant increase in repair and maintenance work on our rental fleet as well as increased costs related to newly set units which experience higher upfront costs than typical run rates and 2) a $2.8 million increase in loss related to the retirement of 263 units. During the year ended December 31, 2021 we had 233 newly set units during the year, of which 51 units were 400 horsepower or larger. Upon initial installation, these units require oil volumes and other materials that exceed general run rate costs. In addition, we experienced higher than normal repair and maintenance needs for our rental fleet during the year. Consistent with our recent shift to a higher horsepower fleet concentration, these large horsepower units are more cost intensive to repair than our legacy fleet. While we have routine repair and maintenance requirements, we believe a large portion of these costs are one-time in nature. These increases were partially offset by higher rental and sales revenues.

Selling, general, and administrative expenses remained relatively unchanged at $10.8 million for the year ended December 31, 2021, as compared to $10.6 million for 2020. This 2.0% increase was primarily the result of increases in health insurance costs.

Depreciation and amortization expense increased to $25.4 million from $25.2 million, or 0.8%, for the year ended December 31, 2021, compared to 2020. The increase is the result of higher capital expenditures for larger horsepower units being added to the fleet. We added 65 units (approximately 18,035 horsepower) to our fleet during the twelve-month period ended December 31, 2021. Twenty-five of those units were 400 horsepower or larger, representing approximately 56% of the horsepower added.

Income tax benefit decreased to $2.6 million from $4.8 million for the year ended December 31, 2021 compared to 2020. Our effective tax rate for both years differs from the U.S. federal statutory rate of 21%. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act ("CARES Act") was enacted in response to the economic impact caused the COVID-19 pandemic. The CARES Act allows federal net operating losses ("NOL") incurred in 2018, 2019, and 2020 to be carried back to each of the five preceding taxable years to generate a refund of previously paid federal income taxes. The Company generated significant NOLs during 2018 and 2019. The Company filed its NOL carryback claims for 2018 and 2019 during 2020. Accordingly, the Company recorded a federal income tax receivable of $15.0 million and an increase to its deferred income tax liability of $10.1 million on its condensed consolidated balance sheet. During the third quarter of 2020, the Company received refunds totaling $3.9 million related to its 2018 NOLs, which, along with year-end provision adjustments, reduced its federal income tax receivable to $11.5 million on its consolidated balance sheet as of December 31, 2021. In addition, the Company recorded a current income tax benefit of $4.8 million on its consolidated statement of operations for the year ended December 31, 2020. Our income tax benefit in 2021 was largely due to our net loss before income taxes of $11.8 million.

Adjusted Gross Margin Year Ended December 31, 2021 Compared to the Year Ended December 31, 2020

The table below shows our adjusted gross margin and related percentages for each of our product lines for the years ended December 31, 2021 and December 31, 2020. Adjusted gross margin is the difference between revenue and cost of revenues, exclusive of depreciation and amortization expense.

Adjusted Gross Margin (1)

Year Ended December 31,

(dollars in thousands)

(1) For a reconciliation of adjusted gross margin to its most directly comparable financial measure calculated and presented in accordance with GAAP, please read "Non-GAAP Financial Measures" below.

Our overall adjusted gross margin percentage decreased to 37.4% for the year ended December 31, 2021 compared to 47.9% for the year ended December 31, 2020, exclusive of depreciation and amortization. Our decrease in gross margins is

28

mainly due to an increase in costs of rentals. While rental revenues increased 4.6% over 2020, our costs of rentals increased 28.5% primarily driven by a significant increase in repair and maintenance work on our rental fleet as well as increased costs related to newly set units which experience higher upfront costs than typical run rates. Rental revenues comprised 88% of our total revenues for the year ended December 31, 2021 compared to 89% of total revenues for the year ended December 31, 2020. While rental activity inherently realizes higher adjusted gross margins, the significant increase in costs of rentals beyond the increase in rental revenues resulted in a large reduction in total gross margins. Sales margin decreased to (13.8)% in 2021 from (9.8)% in 2020. While sales revenues increased 21.7%, this increase was attributable to increased parts sales, which realizes a lower gross margin than compressor sales. While many sales costs are variable, certain costs such as labor are less variable as a certain staff level is retained to meet demand when market forces shift. Third party service and maintenance margins decreased to 53.1% from 54.6% for the year ended December 31, 2021 compared to 2020. Service and maintenance only represents 2.6% of our revenue in 2021, providing minimal impact on our overall adjusted gross margin.

Non-GAAP Financial Measures

Our definition and use of Adjusted EBITDA

“Adjusted EBITDA” is a non-GAAP financial measure that we define as earnings (net (loss) income) before interest, taxes, depreciation and amortization, as well as an increase in inventory allowance and inventory write-offs, retirement of rental equipment and non-cash equity compensation expenses. This term, as used and defined by us, may not be comparable to similarly titled measures employed by other companies and is not a measure of performance calculated in accordance with GAAP. Adjusted EBITDA should not be considered in isolation or as a substitute for operating income, net income or loss, cash flows provided by operating, investing and financing activities, or other income or cash flow statement data prepared in accordance with GAAP. However, management believes Adjusted EBITDA is useful to an investor in evaluating our operating performance because:

•it is widely used by investors in the energy industry to measure a company’s operating performance without regard to items excluded from the calculation of Adjusted EBITDA, which can vary substantially from company to company depending upon accounting methods and book value of assets, capital structure and the method by which assets were acquired, among other factors;

•it helps investors to more meaningfully evaluate and compare the results of our operations from period to period by removing the impact of our capital structure and asset base from our operating structure; and

•it is used by our management for various purposes, including as a measure of operating performance, in presentations to our Board of Directors, as a basis for strategic planning and forecasting, and as a component for setting incentive compensation.

Adjusted EBITDA has limitations as an analytical tool, and you should not consider it in isolation, or as a substitute for analysis of our results as reported under generally accepted accounting principles. Some of these limitations are:

•Adjusted EBITDA does not reflect our cash expenditures, future requirements for capital expenditures, or contractual commitments;

•Adjusted EBITDA does not reflect changes in, or cash requirements for, our working capital needs;

•Adjusted EBITDA does not reflect the cash requirements necessary to service interest or principal payments on our debts; and

•although depreciation and amortization are non-cash charges, the assets being depreciated and amortized will often have to be replaced in the future, and Adjusted EBITDA does not reflect any capital expenditures for such replacements.

There are other material limitations to using Adjusted EBITDA as a measure of performance, including the inability to analyze the impact of certain recurring items that materially affect our net income or loss, and the lack of comparability of results of operations of different companies. Please read the table below under “Reconciliation” to see how Adjusted EBITDA reconciles to our net income, the most directly comparable GAAP financial measure.

29

Reconciliation

The following table reconciles our net (loss) income, the most directly comparable GAAP financial measure, to Adjusted EBITDA:

Year Ended December 31,

(in thousands)

Interest expense 65 14

Retirement of rental equipment 3,096 291

Our definition and use of Adjusted Gross Margin

We define “Adjusted Gross Margin” as total revenue less costs of revenues (excluding depreciation and amortization expense). Adjusted gross margin is included as a supplemental disclosure because it is a primary measure used by our management as it represents the results of revenue and costs (excluding depreciation and amortization expense), which are key components of our operations. Adjusted gross margin differs from gross margin, in that gross margin includes depreciation expense. We believe adjusted gross margin is important because it focuses on the current operating performance of our operations and excludes the impact of the prior historical costs of the assets acquired or constructed that are utilized in those operations. Depreciation expense does not accurately reflect the costs required to maintain and replenish the operational usage of our assets and therefore may not portray the costs from current operating activity. Rather, depreciation expense reflects the systematic allocation of historical property and equipment values over the estimated useful lives.

Adjusted gross margin has certain material limitations associated with its use as compared to gross margin. These limitations are primarily due to the exclusion of depreciation expense, which is material to our results of operations. Because we use capital assets, depreciation expense is a necessary element of our costs and our ability to generate revenue. In order to compensate for these limitations, management uses this non-GAAP measure as a supplemental measure to other GAAP results to provide a more complete understanding of our performance.

As an indicator of our operating performance, adjusted gross margin should not be considered an alternative to, or more meaningful than, gross margin as determined in accordance with GAAP. Our adjusted gross margin may not be comparable to a similarly titled measure of another company because other entities may not calculate adjusted gross margin in the same manner.

30

Reconciliation

The following table calculates gross margin, the most directly comparable GAAP financial measure, and reconciles it to adjusted gross margin:

Year Ended December 31,

(in thousands)

Costs of revenue, exclusive of depreciation and amortization (45,365) (35,431)

Depreciation allocable to costs of revenue (24,753) (24,578)

Depreciation allocable to costs of revenue 24,753 24,578

Liquidity and Capital Resources

Our working capital positions as of December 31, 2021 and 2020 are set forth below.

As of December 31,

(in thousands)

Current Assets:

Prepaid income taxes 51 66

Prepaid expenses and other 854 379

Current Liabilities:

Line of credit — 417

Current operating leases 68 198

For the year ended December 31, 2021, we invested approximately $25.7 million in rental equipment, property and other equipment. During the year, the Company added $24.3 million in new equipment to our rental fleet and $1.4 million in other property and equipment. Our investment in rental equipment includes any changes to work-in-progress related to our rental fleet jobs at the beginning of the year compared to the end of the year. Our rental work-in-progress increased by $1.4 million during 2021. We financed our investment in rental equipment, property and other equipment with cash flows from operations during 2021. We anticipate that our cash flows from operations as well as our borrowing capacity under our New Credit Agreement will provide ample liquidity for our planned capital expenditures during 2022 and beyond.

Cash flows

At December 31, 2021, we had cash and cash equivalents of $22.9 million compared to $28.9 million at year end 2020. Our cash flow from operations of $28.5 million was partially offset by capital expenditures of $25.7 million during 2021. In addition, we expended $7.9 million in connection with our share repurchase program. We also had working capital of $44.8

31

million at December 31, 2021 compared to $61.9 million at December 31, 2020. We had net cash flow from operating activities of $28.5 million during 2021 compared $32.6 million during 2020. Our cash flow from operating activities of $28.5 million was primarily the result of our rental and sales gross margins.

At December 31, 2020, we had cash and cash equivalents of $28.9 million, working capital of $61.9 million and total debt of $417,000, under our credit agreement which was due on March 31, 2021. We had positive net cash flow from operating activities of approximately $32.6 million during 2020.

Senior Bank Borrowings

Previous Credit Agreement

We had a senior secured revolving credit agreement (the "Previous Credit Agreement") with JP Morgan Chase Bank, N.A (the "Lender") that matured on March 31, 2021. Prior to maturation, the outstanding balance of $417,000 was repaid. The Previous Credit Agreement had an aggregate commitment of $30 million, subject to collateral availability.

New Credit Agreement

On May 11, 2021, we entered into a five-year senior secured revolving credit agreement ("New Credit Agreement") with Texas Capital Bank, National Association (the "Lender") with an initial commitment of $20 million and an accordion feature that would increase the maximum commitment to $30 million, subject to collateral availability. We also have a right to request from the Lender, on an uncommitted basis, an increase of up to $30 million on the aggregate commitment; provided, however, the aggregate commitment amount is not permitted to exceed $50 million. The maturity date of the New Credit Agreement is May 11, 2026. The obligations under the New Credit Agreement are secured by a first priority lien on a variety of our assets, including inventory and accounts receivable as well as a variable number of our leased compressor equipment.

Borrowing Base. At any time before the maturity of the New Credit Agreement, we may draw, repay and re-borrow amounts available under the borrowing base up to the maximum aggregate availability discussed above. Generally, the borrowing base equals the sum of (a) 90% of eligible accounts receivable owed to the Company by investment grade debtors, plus (b) 85% of the eligible accounts receivable owing by non-investment grade debtors, plus (c) 50% of the eligible inventory, valued at the lower of cost or market value at such time, subject to a cap of this component not to exceed $2 million, plus (d) the lesser of (i) 95% of the net book value of the compressors that the Lender has determined are eligible for the extension of credit, valued at the lower of cost or market value with depreciation not to exceed 25 years, at such time and (ii) 80% of the net liquidation value percentage of the net book value of the eligible compressors that the Lender has determined are eligible for the extension of credit, valued at the lower of cost or market value with depreciation not to exceed 25 years, at such time, plus (e) 80% of the value at cost (excluding any costs for capitalized interest or other non-cash capitalized costs) of the eligible new compressor fleet, minus (f) any required availability reserves determined by the Lender in its sole discretion. The Lender may adjust the borrowing base components if material deviations in the collateral are discovered in future audits of the collateral. As of December 31, 2021, our allowable borrowing base was $20.0 million.

Interest and Fees. Under the terms of the New Credit Agreement, we have the option of selecting the applicable variable rate for each revolving loan, or portion thereof, of either (a) the Base Rate (as defined below) plus the Applicable Margin, or (b) in the case of a Eurodollar Rate Loan, the Adjusted Eurodollar Rate plus the Applicable Margin. "Base Rate" means, for any day, a rate of interest per annum equal to the highest of (a) the prime rate for such day; (b) the sum of the federal funds rate for such day plus 0.50%; and (c) the Adjusted Eurodollar Rate for such day plus 1.00%. The Applicable Margin is determined based upon the leverage ratio as set forth in the most recent compliance certificate received by the Lender for each fiscal quarter from time to time pursuant to the New Credit Agreement. Depending on the leverage ratio, the Applicable Margin can be 0.25% to 0.75% for Base Rate Loans (as defined in the New Credit Agreement) and 1.25% to 1.75% for Eurodollar Rate Loans and for requested letters of credit. In addition, we are required to pay a monthly commitment fee on the daily average unused amount of the commitment while the New Credit Agreement is in effect at an annual rate equal to 0.25% of the unused commitment amount. Accrued interest is payable monthly on outstanding principal amounts and unused commitment fee, provided that accrued interest on Eurodollar Rate Loans is payable at the end of each interest period, but in no event less frequently than quarterly.

Covenants. The New Credit Agreement contains customary representations and warranties, as well as covenants which, among other things, condition or limit our ability to incur additional indebtedness and liens; enter into transactions with affiliates; make acquisitions in excess of certain amounts; pay dividends; redeem or repurchase capital stock or senior notes; make investments or loans; make negative pledges; consolidate, merge or effect asset sales; or change the nature of our business. In addition, we also have certain financial covenants that are applicable during certain trigger periods specified in the Credit Agreement and require us during such trigger periods to maintain a leverage ratio less than or equal to 3.00 to 1.00 as of the last day of each fiscal quarter and a fixed charge coverage ratio greater than or equal to 1.00 to 1.00 as of the last day of each fiscal quarter.

Events of Default and Acceleration. The New Credit Agreement contains customary events of default for credit facilities of this size and type, and includes, without limitation, payment defaults; defaults in performance of covenants or other

32

agreements contained in the Credit Agreement and the other transaction documents; inaccuracies in representations and warranties; certain defaults, termination events or similar events; certain defaults with respect to any other Company indebtedness in excess of $1.0 million; certain bankruptcy or insolvency events; the rendering of certain judgments in excess of $1.0 million; certain ERISA events; certain change in control events and the defectiveness of any liens under the secured revolving credit agreement. Obligations outstanding under the Credit Agreement may be accelerated upon the occurrence of an event of default.

As of December 31, 2021, we were in compliance with all financial covenants in our New Credit Agreement. At December 31, 2021, we had no amounts outstanding under the New Credit Agreement.

Components of Our Principal Capital Expenditures

Capital expenditures for the years ended December 31:

(in thousands)

Rental equipment and property and equipment $ 25,710 $ 15,257

The level of our expenditures will vary in future periods depending on energy market conditions and other related economic factors. Based upon existing economic and market conditions, we believe that our cash on hand, operating cash flow and available line of credit are adequate to fully fund our net capital expenditures requirements for 2022. We also believe we have flexibility with respect to our financing alternatives and adjustments to our capital expenditure plans if circumstances warrant. We do not have any material continuing commitments related to our current operations that cannot be met with our cash on hand and our line of credit. However, our financing capacity could be negatively impacted by the COVID-19 pandemic. Please see Item 1A, Risk Factors, of this report.

Off-Balance Sheet Arrangements

From time-to-time, we enter into off-balance sheet arrangements and transactions that can give rise to off-balance sheet obligations. As of December 31, 2021, we did not have any material off-balance sheet arrangements.

Recently Issued Accounting Pronouncements

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform, which provides temporary optional guidance to companies impacted by the transition away from the London Interbank Offered Rate ("LIBOR"). The guidance provides certain expedients and exceptions to applying GAAP in order to lessen the potential accounting burden when contracts, hedging relationships and other transactions that reference LIBOR as a benchmark rate are modified. This guidance is effective upon issuance and expires on December 31, 2022. We are currently evaluating the impact of the LIBOR transition and this ASU 2020-04 on our consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (ASC Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments to ASC Topic 326 require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, including trade receivables. For companies that qualify as smaller reporting companies, the amendments in this update are effective for interim and annual periods beginning after January 1, 2023. We are currently evaluating the impact of ASU 2016-13 on our consolidated financial statements and note disclosures.

Environmental Regulations

Various federal, state and local laws and regulations covering the discharge of materials into the environment, or otherwise relating to protection of human safety and health and the environment, affect our operations and costs. Compliance with these laws and regulations could cause us to incur remediation or other corrective action costs or result in the assessment of administrative, civil and criminal penalties and the issuance of injunctions delaying or prohibiting operations. In addition, we have acquired certain properties and plant facilities from third parties whose actions with respect to the management and disposal or release of hydrocarbons or other wastes were not under our control. Under environmental laws and regulations, we could be required to remove or remediate wastes disposed of or released by prior owners. In addition, we could be responsible under environmental laws and regulations for properties and plant facilities we lease, but do not own. Compliance with such laws and regulations increases our overall cost of business, but has not had a material adverse effect on our operations or financial condition. It is not anticipated, based on current laws and regulations, that we will be required in the near future to expend amounts that are material in relation to our total expenditure budget in order to comply with environmental laws and regulations but such laws and regulations are frequently changed and we are unable to predict the ultimate cost of

33

compliance. We also could incur costs related to the cleanup of sites to which we send equipment and for damages to natural resources or other claims related to releases of regulated substances at such sites.

ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA

Our consolidated financial statements and supplementary financial data are included in this Annual Report on Form 10-K beginning on page F-1.

ITEM 9. CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND FINANCIAL DISCLOSURE

None.

ITEM 9A. CONTROLS AND PROCEDURES

Evaluation of Disclosure Controls and Procedures

An evaluation was carried out under the supervision and with the participation of our management, including our President and Chief Executive Officer and our Vice President and Chief Financial Officer, of the effectiveness of the design of our “disclosure controls and procedures” (as such term is defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended or, the “Exchange Act”) as of December 31, 2021, pursuant to Exchange Act Rule 13a-15. Based upon that evaluation, the President and Chief Executive Officer and our Vice President and Chief Financial Officer concluded that our disclosure controls and procedures as of December 31, 2021, are effective to ensure that information required to be disclosed by us in the reports filed or submitted by us under the Exchange Act is recorded, processed, summarized, and reported within the time periods specified in the SEC's rules and forms and include controls and procedures designed to ensure that information required to be disclosed by us in such reports is accumulated and communicated to our management, including our principal executive and financial officers as appropriate to allow timely decisions regarding required disclosures. Due to the inherent limitations of control systems, not all misstatements may be detected. Those inherent limitations include the realities that judgments in decision-making can be faulty and that breakdowns can occur because of simple errors or mistakes. Additionally, controls could be circumvented by the individual acts of some persons or by collusion of two or more people. Our controls and procedures can only provide reasonable, not absolute, assurance that the above objectives have been met.

Management’s Report on Internal Control Over Financial Reporting

Our management, including the President and Chief Executive Officer and our Principal Accounting Officer, is responsible for establishing and maintaining adequate internal control over financial reporting, as defined in Rule 13a-15(f) and 15d-15(f) under the Exchange Act. Our internal control system is designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. Our internal control over financial reporting includes those policies and procedures that:

•pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of our assets;

•provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with accounting principles generally accepted in the United States of America, and that our receipt and expenditures are being made only in accordance with authorizations of management and our Board of Directors; and

•provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of our assets that could have a material effect on the financial statements.

All internal control systems, no matter how well designed, have inherent limitations. A system of internal control may become inadequate over time because of changes in conditions or deterioration in the degree of compliance with the policies or procedures. Therefore, even those systems determined to be effective can provide only reasonable assurance with respect to financial statement preparation and presentation.

A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of our annual or interim financial statements will not be prevented or detected on a timely basis.

34

Management, including our President and Chief Executive Officer and our Vice President and Chief Financial Officer, assessed the effectiveness of the Company’s internal control over financial reporting as of December 31, 2021. In making this assessment, management used the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission (COSO) in Internal Control—Integrated Framework (2013). Based on this assessment, management has concluded that our internal control over financial reporting was effective as of December 31, 2021.

Changes in Internal Control Over Financial Reporting

There were no changes in our internal control over financial reporting that occurred during the year ended December 31, 2021, that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting. We will continue to review and document our disclosure controls and procedures, including our internal control over financial reporting, and may from time to time make changes aimed at enhancing their effectiveness and to ensure that our systems evolve with our business.

ITEM 9B. OTHER INFORMATION

None.

ITEM 9C. DISCLOSURES REGARDING FOREIGN JURISDICTIONS THAT PREVENT INSPECTIONS

None.

35

PART III

ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE

The information required by this item is incorporated herein by reference to the sections “Election of Directors,” “Executive Officers,” “Corporate Governance” and “The Board of Directors and its Committees” in our definitive proxy statement which will be filed with the Securities and Exchange Commission within 120 days after December 31, 2021 or as such period may be extended by action of the Securities and Exchange Commission.

We have adopted a Code of Business Conduct and Ethics that applies to our directors, officers and employees. The Code of Business Conduct and Ethics is posted in the "Investor Relations" section of our website at www.ngsgi.com. The Code of Business Conduct and Ethics maybe obtained free of charge by writing before to Natural Gas Services Group, Inc., Attn: Investor Relations, 404 Veterans Airpark Lane, Ste 300 Midland, TX 79705.

ITEM 11. EXECUTIVE COMPENSATION

The information required by this item is incorporated herein by reference to the section “Executive Compensation” in our definitive proxy statement which will be filed with the Securities and Exchange Commission within 120 days after December 31, 2021 or as such period may be extended by action of the Securities and Exchange Commission.

ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT AND RELATED STOCKHOLDER MATTERS

The information required by this item is incorporated herein by reference to the section “Principal Shareholders and Security Ownership of Management” in our definitive proxy statement which will be filed with the Securities and Exchange Commission within 120 days after December 31, 2021 or as such period may be extended by action of the Securities and Exchange Commission.

ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS, AND DIRECTORINDEPENDENCE

The information required by this item is incorporated herein by reference to the sections “Related Person Transactions” and “Corporate Governance” in our definitive proxy statement which will be filed with the Securities and Exchange Commission within 120 days after December 31, 2021 or as such period may be extended by action of the Securities and Exchange Commission.

ITEM 14. PRINCIPAL ACCOUNTING FEES AND SERVICES

The information required by this item is incorporated herein by reference to the section “Principal Accounting Fees and Services” in our definitive proxy statement which will be filed with the Securities and Exchange Commission within 120 days after December 31, 2021 or as such period may be extended by action of the Securities and Exchange Commission.

36

PART IV

ITEM 15. EXHIBITS AND CONSOLIDATED FINANCIAL STATEMENTS

The following documents are filed as part of this Annual Report on Form 10-K:

(a)(1) and (a)(2) Consolidated Financial Statements

For a list of Consolidated Financial Statements, see “Index to Consolidated Financial Statements” incorporated herein by reference.

(a)(3) Exhibits

A list of exhibits to this Annual Report on Form 10-K is set forth below:

Exhibit No.Description

37

*21.1 Subsidiaries of the registrant

*23.1 Consent of Moss Adams LLP

101.INS XBRL Instance Document

101.SCH XBRL Taxonomy Extension Schema Document

101.CAL XBRL Taxonomy Extension Calculation Linkbase Document

101.DEF XBRL Taxonomy Extension Definition Linkbase Document

101.LAB XBRL Taxonomy Extension Label Linkbase Document

101.PRE XBRL Taxonomy Extension Presentation Linkbase Document

* Filed herewith.

ITEM 16. FORM 10-K SUMMARY

None.

38

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

NATURAL GAS SERVICES GROUP, INC.

March 18, 2022 By: /s/ Stephen C. Taylor

Stephen C. Taylor

Chairman of the Board, President and Chief Executive Officer

(Principal Executive Officer)

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Stephen C. Taylor and Micah C. Foster, jointly and severally, as his/her true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution, for him/her and in his/her name, place and stead, in any and all capacities, to sign any and all amendments to this Annual Report on Form 10-K and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises hereby ratifying and confirming all that said attorneys-in-fact and agents, or his substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated:

Signature Title Date

Stephen C. Taylor

Micah C. Foster

/s/ Leslie A. Beyer Director March 18, 2022

Leslie A. Beyer

/s/ Nigel J. Jenvey Director March 18, 2022

Nigel J. Jenvey

/s/ David L. Bradshaw Director March 18, 2022

David L. Bradshaw

/s/ John W. Chisholm Director March 18, 2022

John W. Chisholm

39

INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

Page

Consolidated Balance Sheets as of December 31, 2021 and 2020 F-2

Notes to Consolidated Financial Statements F-6

38

Report of Independent Registered Public Accounting Firm

To the Shareholders and the Board of Directors of

Natural Gas Services Group, Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Natural Gas Services Group, Inc. and subsidiary (the “Company”) as of December 31, 2021 and 2020, and the related consolidated statements of operations, stockholders’ equity, and cash flows for each of the years then ended, and the related notes (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the consolidated financial position of the Company as of December 31, 2021 and 2020, and the consolidated results of its operations and its cash flows for the year then ended, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These consolidated financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s consolidated financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) ("PCAOB") and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audit we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company's internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. We believe that our audit provides a reasonable basis for our opinion.

Critical Audit Matter

Critical audit matters are matters arising from the current period audit of the consolidated financial statements that were communicated or required to be communicated to the audit committee and that (1) relate to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. We determined that there are no critical audit matters.

/s/ Moss Adams LLP

Dallas, Texas

March 18, 2022

We have served as the Company's auditor since 2020.

F - 1

NATURAL GAS SERVICES GROUP, INC.CONSOLIDATED BALANCE SHEETS(in thousands)

December 31,

ASSETS

Current Assets:

Prepaid income taxes 51 66

Prepaid expenses and other 854 379

LIABILITIES AND STOCKHOLDERS' EQUITY

Current Liabilities:

Line of credit — 417

Current operating leases 68 198

Long-term operating leases 217 285

Commitments and contingencies (Note 14)

Stockholders’ Equity:

Preferred stock, 5,000 shares authorized, no shares issued or outstanding — —

Treasury shares, at cost, 775 shares and 38, respectively (8,344) (490)

Total liabilities and stockholders' equity $ 298,506 $ 306,801

See accompanying notes to these consolidated financial statements.

F - 2

For the Years Ended December 31,

Revenue:

Service and maintenance income 1,914 1,572

Operating costs and expenses:

Cost of rentals, exclusive of depreciation stated separately below 36,638 28,506

Cost of sales, exclusive of depreciation stated separately below 7,829 6,211

Selling, general and administrative expenses 10,762 10,550

Retirement of rental equipment 3,096 291

Other income (expense):

Interest expense (65) (14)

Total other income, net 622 615

(Provision for) benefit from income taxes:

Earnings (loss) per share:

Weighted average shares outstanding:

See accompanying notes to these consolidated financial statements.

F - 3

NATURAL GAS SERVICES GROUP, INC.

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

(in thousands)

Shares Amount Shares Amount Shares Amount

Compensation expense on common stock options — — — — 19 — — — 19

Issuance of restricted stock — — 118 — — — — — —

Compensation expense on restricted common stock — — — 1 2,175 — — — 2,176

Compensation expense on common stock options — — — — 1 — — — 1

Issuance of restricted stock — — 98 — — — — — —

Compensation expense on restricted common stock — — — 1 1,737 — — — 1,738

Purchase of treasury shares — — — — — — 737 (7,854) (7,854)

See accompanying notes to these consolidated financial statements.

F - 4

For the Years Ended December 31,

CASH FLOWS FROM OPERATING ACTIVITIES:

Amortization of debt issuance costs 31 —

Gain on disposal of assets (182) (284)

Retirement of rental equipment 3,096 291

Gain on company owned life insurance (298) (168)

Changes in operating assets and liabilities:

Prepaid income taxes and prepaid expenses (460) (11,346)

Accounts payable and accrued liabilities 9,756 4,880

NET CASH PROVIDED BY OPERATING ACTIVITIES 28,527 32,649

CASH FLOWS FROM INVESTING ACTIVITIES:

Purchase of rental equipment, property and other equipment (25,710) (15,257)

Purchase of company owned life insurance (150) (296)

Proceeds from sale of property and equipment 195 394

NET CASH USED IN INVESTING ACTIVITIES (25,665) (15,159)

CASH FLOWS FROM FINANCING ACTIVITIES:

Proceeds of other long-term liabilities (1) (5)

Repayments of line of credit, net (417) —

Payments of debt issuance costs (237) —

Purchase of treasury shares (7,854) —

Taxes paid related to net share settlement of equity awards (336) (152)

NET CASH USED IN FINANCING ACTIVITIES (8,845) (157)

NET CHANGE IN CASH AND CASH EQUIVALENTS (5,983) 17,333

CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD 28,925 11,592

CASH AND CASH EQUIVALENTS AT END OF PERIOD $ 22,942 $ 28,925

SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:

Interest paid $ 30 $ 14

Income taxes paid — 105

NON-CASH TRANSACTIONS

Right of use asset acquired through an operating lease — 77

See accompanying notes to these consolidated financial statements.

F - 5

NATURAL GAS SERVICES GROUP INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1. Description of Business

Natural Gas Services Group, Inc. (the "Company", “NGS”, "Natural Gas Services Group", "we" or "our") (a Colorado corporation), is a leading provider of natural gas compression equipment and services to the energy industry. The Company manufactures, fabricates, rents, sells and maintains natural gas compressors and flare systems for oil and natural gas production and plant facilities. NGS is headquartered in Midland, Texas, with fabrication facilities located in Tulsa, Oklahoma and Midland, Texas, and service facilities located in major oil and natural gas producing basins in the U.S. The Company was formed on December 17, 1998.

2. Summary of Significant Accounting Policies

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company, its subsidiary, NGSG Properties, LLC and the rabbi trust associated with the Company’s deferred compensation plan, see Note 10. All significant intercompany accounts and transactions for the periods presented have been eliminated in consolidation.

Use of Estimates

The preparation of our consolidated financial statements in conformity with generally accepted accounting principles in the United States of America requires our management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Significant estimates include fixed asset lives, bad debt allowance and the allowance for inventory obsolescence. Additionally, NGS conducts a yearly review of impairment of long-lived assets. Throughout the review, determining factors are based on estimates that can significantly impact the carrying value of these assets. It is at least reasonably possible these estimates could be revised in the near term and the revisions could be material.

Cash Equivalents and Financial Instruments

For purposes of reporting cash flows, we consider all short-term investments with an original maturity of three months or less to be cash equivalents. We invest our cash primarily in deposits and money market funds with commercial banks. At times, cash balances at banks and financial institutions may exceed federally insured amounts. We believe that the risk to our cash balance is minimal because we have chosen a large regional bank with strong long-term ratings of Baa3/BBB-.

Accounts Receivable

Our trade receivables consist of customer obligations for the sale of compressors and flare systems due under normal trade terms, and operating leases for the use of our natural gas compressors. The receivables are not collateralized except as provided for under lease agreements. However, we typically require deposits of as much as 50% or use of progress payments for large custom sales contracts. We perform ongoing credit evaluations of our customers and adjust credit limits based on management's assessment of the customer's financial condition and payment history, as well as industry conditions and general economic conditions. We continuously monitor collections and payments from our customers, and maintain a provision for estimated credit losses based upon our historical experience and any specific customer collection issues that we have identified. While such credit losses have historically been within our expectations and the provisions established, we cannot guarantee that we will continue to experience the same credit loss rates that we have in the past. One customer accounted for 46% and 35% of our accounts receivable as of December 31, 2021 and 2020, respectively. A significant change in the liquidity or financial position of this customer could have a material adverse impact on the collectability of our accounts receivable and our future operating results. The allowance for doubtful accounts was $1.1 million and $1.2 million at December 31, 2021 and 2020, respectively. Management believes that the allowance is adequate; however, actual write-offs may exceed the recorded allowance.

F - 6

A summary of our allowance for doubtful accounts is as follows:

Year Ended December 31,

Recoveries 8 —

Revenue Recognition Policy

Revenue is measured based on a consideration specified in a customer’s contract, excluding any sale incentives and taxes collected on behalf of third parties (i.e. sales and property taxes). Revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration that we expect to receive for those goods or services. To recognize revenue, we (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, we satisfy the performance obligation(s). Shipping and handling costs incurred are accounted for as fulfillment costs and are included in cost of revenues in our Consolidated Statements of Operations.

Nature of Goods and Services

The following is a description of principal activities from which the Company generates its revenue:

Rental Revenue. The Company generates revenue from renting compressors and flare systems to our customers. These contracts, which all qualify as operating leases under ASC Topic 842, Leases (ASC 842), may also include a fee for servicing the compressor or flare during the rental contract. Our rental contracts typically range from six to 24 months, with our larger horsepower compressors having contract terms of up to 60 months. Our revenue is recognized over time, with equal monthly payments over the term of the contract. After the terms of the contract have expired, a customer may renew their contract or continue renting on a monthly basis thereafter. In accordance ASC 842 – Leases, we have applied the practical expedient ASC 842-10-15-42A, which allows the Company to combine lease and non-lease components.

Sales Revenue. The Company generates revenue by the sale of custom/fabricated compressors, flare systems and parts, as well as, exchange/rebuilding customer owned compressors and sale of used rental equipment.

Custom/fabricated compressors and flare systems - The Company designs and fabricates compressors and flares based on the customer’s specifications outlined in their contract. Though the equipment being built is customized by the customer, control under these contracts does not pass to the customer until the compressor or flare package is completed and shipped, or in accordance with a bill and hold arrangements the customer accepts title and assumes the risk and rewards of ownership. We request some of our customers to make progressive payments as the product is being built; these payments are recorded as a contract liability on the Deferred Income line on the consolidated balance sheet until control has been transferred. These contracts also may include an assurance warranty clause to guarantee the product is free from defects in material and workmanship for a set duration of time; this is a standard industry practice and is not considered a performance obligation.

From time to time, upon the customer’s written request, we recognize revenue when manufacturing is complete and the equipment is ready for shipment. At the customer’s request, we will bill the customer upon completing all performance obligations, but before shipment. The customer will formally request we ship the equipment per their direction from our manufacturing facility at a later specified date and that we segregate the equipment from our finished goods, such that they are not available to fill other orders. Per the customer’s agreement change of control is passed to the customer once the equipment is complete and ready for shipment. We have operated using bill and hold agreements with certain customers for many years, with consistent satisfactory results for both the customer and us. The credit terms on these agreements are consistent with the credit terms on all other sales. All control is shouldered by the customer and there are no exceptions to the customer’s commitment to accept and pay for the manufactured equipment. Revenues recognized related to bill and hold arrangements for the years ended December 31, 2021 and 2020 was approximately $20,000 and $852,000, respectively.

Parts - Revenue is recognized after the customer obtains control of the parts. Control is passed either by the customer taking physical possession or the parts being shipped. The amount of revenue recognized is not adjusted for expected returns, as our historical part returns have been de minimis.

F - 7

Exchange or rebuilding customer owned compressors - Based on the contract, the Company will either exchange a new/rebuilt compressor for the customer’s malfunctioning compressor or rebuild the customer’s compressor. Revenue is recognized after control of the replacement compressor has transferred to the customer based on the terms of the contract, i.e., by physical delivery, delivery and installment, or shipment of the compressor.

Used compressors or flares - From time to time, a customer may request to purchase a used compressor or flare out of our rental fleet. Revenue from the sale of rental equipment is recognized when the control has passed to the customer based on the terms of the contract, i.e. when the customer has taken physical possession or the equipment has been shipped.

Service and Maintenance Revenue. The Company provides routine or call-out services on customer owned equipment. Revenue is recognized after services in the contract are rendered.

Payment terms for sales revenue and service and maintenance revenue discussed above are generally 30 to 60 days although terms for specific customers can vary. Also, the transaction prices are not subject to variable consideration constraints.

Disaggregation of Revenue

The following table shows the Company's revenue disaggregated by product or service type for the years ended:

Year Ended December 31,

(in thousands)

Other (Parts/Rebuilds) - sales 4,626 2,957

Total revenue from contracts with customers 8,796 7,229

Contract Balances

As of December 31, 2021 and 2020, we had the following receivables and deferred income from contracts with customers:

December 31,

(in thousands)

Accounts Receivable

Accounts receivable - contracts with customers $ 3,354 $ 3,243

Less: Allowance for doubtful accounts (1,129) (1,161)

The Company recognized $1.1 million in revenue for the year ended December 31, 2021 that was included in deferred income at the beginning of 2021. For the period ended December 31, 2020, the Company recognized revenue of $73,000 from amounts related to sales that were included in deferred income at the beginning of 2020.

The increases (decreases) of accounts receivable and deferred income were primarily due to normal timing differences between our performance and the customers’ payments.

F - 8

Transaction Price Allocated to the Remaining Performance Obligations

As of December 31, 2021, the Company did not have revenue related to unsatisfied performance obligations.

Contract Costs

The Company recognizes the incremental costs of obtaining contracts as an expense when incurred if the amortization period of the assets that the Company otherwise would have recognized is one year or less. These costs are included in selling, general and administrative expense on our Consolidated Statements of Operations.

Leases

Accounting Standards Codification ("ASC") 842 requires all leases to be reported on the balance sheet as right-of-use ("ROU") assets and lease obligations. We determine if an arrangement is a lease at inception and determine lease classification and recognize ROU assets and liabilities on the lease commencement date based on the present value of lease payments over the lease term. As the discount rate implicit in the lease is rarely readily determinable, we estimate our incremental borrowing rate using information available at the commencement date in determining the present value of the lease payments. We, as a lessee, apply the practical expedient to not separate non-lease components from lease components, therefore, accounting for each separate lease component and its associated non-lease component, as a single lease component. For each lease that 1) contains the same timing and pattern of transfer for lease and non-lease components and 2) if the lease component, if accounted for separately, would be classified as an operating lease, the Company has elected to not separate non-lease components from lease components.

Major Customers and Concentration of Credit Risk

Sales and rental income from Occidental Permian, LTD. ("Oxy") in 2021 and 2020 amounted to 40% and 30% of revenue, respectively. No other single customer accounted for more than 10% of our revenues in 2021 and 2020. Oxy's accounts receivable balances amounted to 46% and 35% of our accounts receivable as of December 31, 2021 and 2020, respectively. No other customers amounted to more than 10% of our accounts receivable as of December 31, 2021 and 2020.

Inventory

Inventory (current and long-term) is valued at the lower of cost and net realizable value. The cost of inventories is determined by the weighted average method. We regularly review inventory quantities on hand and record a provision for excess and obsolete inventory based primarily on current and anticipated customer demand and production requirements. The Company assesses anticipated customer demand based on current and upcoming capital expenditure budgets of its major customers as well as other significant companies in the industry, along with oil and natural gas price forecasts and other factors affecting the industry. In addition, our long-term inventory consists of raw materials and replacement parts that remain viable but which the Company does not expect to sell within the next year.

Rental Equipment and Property and Equipment

Rental equipment and property and equipment are recorded at cost less accumulated depreciation, except for work-in-progress on new rental equipment which is recorded at cost until it’s complete and added to the fleet. Depreciation is computed using the straight-line method over the estimated useful lives of the assets. Our rental equipment has an estimated useful life between 15 and 25 years, while our property and equipment has an estimate useful lives which range from 3 to 39 years. The majority of our property and equipment, including rental equipment, is a direct cost to generating revenue.

We assess the impairment of rental equipment and property and equipment whenever events or changes in circumstances indicate that the net recorded amount may not be recoverable. The following factors could trigger an impairment review: significant underperformance relative to historical or projected future cash flows; significant adverse changes in the extent or manner in which asset (or asset group) is being used or its condition, including a meaningful drop in fleet utilization over the prior four quarters; significant negative industry or company-specific trends or actions, including meaningful capital expenditure budget reductions by our major customers or other sizable exploration and production or midstream companies, as well as significant declines in oil and natural gas prices; legislative changes prohibiting us from leasing our units or flares; or poor general economic conditions. An impairment loss is recognized if the future undiscounted cash flows associated with the asset (or asset group) and the estimated fair value of the asset are less than the asset's carrying value.

F - 9

Sales of equipment out of the rental fleet are included with sales revenue and cost of sales, while retirements of units are shown a separate operating expense. Gains and losses resulting from sales and dispositions of other property and equipment are included with other income. Maintenance and repairs are charged to cost of rentals as incurred.

Intangibles

At December 31, 2021 and 2020, NGS had intangible assets, which relate to developed technology and a trade name. Developed technology is amortized on a straight-line basis with a useful life of 20 years, with a weighted average remaining life of approximately four years as of December 31, 2021. NGS has an intangible asset related to the trade name of SCS which was acquired in our acquisition of Screw Compression Systems in January 2005. This asset is not being amortized as it has been deemed to have an indefinite life.

Our policy is to review intangibles that are being amortized for impairment when indicators of impairment are present. In addition, it is our policy to review indefinite-lived intangible assets for impairment annually or when indicators of impairment are present. We review intangibles through an assessment of the estimated future cash flows related to such assets. In the event that assets are found to be carried at amounts in excess of estimated undiscounted future cash flows, then the assets will be adjusted for impairment to a level commensurate with a discounted cash flow analysis of the underlying assets.

Warranty

When warranted, we accrue amounts for estimated warranty claims based upon current and historical product warranty costs and any other related information known. There was no warranty reserve as of December 31, 2021 and 2020.

Income Taxes

Deferred tax assets and liabilities are recognized for the future tax consequences attributable to temporary differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases, and operating losses and tax credit carry-forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. We assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe that recovery is not probable, we establish a valuation allowance. To the extent we establish a valuation allowance or increase this allowance in a period, we include an expense in the tax provision in the statement of income.

ASC Topic 740 prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. In order to record any financial statement benefit, we are required to determine, based on technical merits of the position, whether it is more likely than not (a likelihood of more than 50 percent) that a tax position will be sustained upon examination, including resolution of any related appeals or litigation processes. If that step is satisfied, then we must measure the tax position to determine the amount of benefit to recognize in the financial statements. The tax position is measured at the largest amount of the benefit that is greater than 50 percent likely of being realized upon ultimate settlement.

Our policy regarding income tax interest and penalties is to expense those items as other expense.

We account for uncertain tax positions in accordance with guidance in FASB ASC 740, which prescribes the minimum recognition threshold a tax position taken or expected to be taken in a tax return is required to meet before being recognized in the financial statements. We have no uncertain tax positions as of December 31, 2021.

Fair Value Measurement

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date under current market conditions. ASC Topic 820 established a fair value hierarchy, which requires an entity to maximize the use of observable inputs when measuring fair value. These inputs are categorized as follows:

Level 1- quoted prices in an active market for identical assets or liabilities;

F - 10

Level 2- quoted prices in an active market for similar assets or liabilities, inputs other than quoted prices that are observable for similar assets or liabilities, inputs derived principally from or corroborated by observable market data by correlation or other means; and