Securities registered pursuant to section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes o    No x

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o    No x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x    No o

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 229.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes x    No o

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§ 229.405 of this chapter) is not contained herein, and will not be contained, to the best of registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. o

Indicate by check mark whether the registrant is a shell company (as defined by Rule 12b-2 of the Act). Yes o    No x

The aggregate market value of the voting stock held by non-affiliates of the registrant as of June 30, 2016, the last business day of the registrant's most recently completed second fiscal quarter, was approximately $338,632,713 (computed by reference to the price at which the registrant's common stock was last sold on such date, as reported by The NASDAQ Global Select Market). Shares of common stock held by the registrant's officers and directors and holders of 10% or more of the outstanding shares of the registrant's common stock have been excluded from the calculation of this amount because such persons may be deemed to be affiliates; however, this determination of affiliate status is not, and shall not be considered, a determination of affiliate status for any other purpose.

As of February 28, 2017, the number of outstanding shares of the registrant's common stock was 149,591,164.

Portions of the registrant's definitive proxy statement for its 2017 annual meeting of stockholders are incorporated in Part III of this report by reference to the extent stated therein.

For the Fiscal Year Ended December 31, 2016

Unless the context indicates otherwise, all references to "Clean Energy," the "Company," "we," "us," or "our" in this report refer to Clean Energy Fuels Corp., together with its majority and wholly owned subsidiaries. Although we do not use the “™” symbol in each instance in which one of our common law trademarks appears in this report, we own unregistered trademark rights to Redeem^™, NGV Easy Bay^™, Clean Energy^™, Clean Energy Renewables^™, Clean Energy Compression^™ and Clean Energy Cryogenics^™.

We serve fleet vehicle operators in a variety of markets, including heavy-duty trucking, airports, refuse, public transit, government fleets, and industrial and institutional energy users. We believe these fleet markets will continue to present a growth opportunity for natural gas vehicle fuel for the foreseeable future. As of December 31, 2016, we serve nearly 1,000 fleet customers operating over 45,000 natural gas vehicles and we own, operate or supply over 570 natural gas fueling stations in 42 states in the United States and four provinces in Canada.

As of December 31, 2016, Natural Gas Vehicles for America ("NGV America") estimates that there were approximately 1,750 natural gas fueling stations in the United States and about 153,000 natural gas vehicles on American roads, including 39,500 heavy-duty vehicles (e.g. tractors, refuse trucks and buses), 25,800 medium-duty vehicles (e.g. delivery vans and shuttles) and 87,000 light-duty vehicles (e.g. passenger cars, small utility vehicles, trucks and vans).

Domestic and Plentiful Supply.    Technological advances in natural gas drilling and production, including the widespread deployment of horizontal drilling techniques and the use of hydraulic fracturing, have unlocked vast natural gas reserves. The United States produces the highest volume of natural gas in the world, with proven, abundant and growing reserves of natural gas.

Less Expensive.    Due to the abundance of natural gas, the cost of natural gas in the United States is less than the cost of crude oil, on an energy equivalent basis. Based on projections from the U.S. Energy Information Administration, we believe that natural gas will remain cheaper than gasoline and diesel for the foreseeable future. In addition, because the price of the natural gas commodity makes up a smaller portion of the cost of a GGE of CNG or LNG relative to the commodity portion of the cost of a GGE of diesel or gasoline, the price of a GGE of CNG or LNG is less sensitive to increases in the underlying commodity cost.

Cleaner.    Natural gas contains less carbon than any other fossil fuel and thus produces fewer carbon dioxide emissions when burned.  The California Air Resources Board ("CARB") has concluded that a natural gas vehicle emits fewer greenhouse gas emissions than a comparable gasoline or diesel fueled vehicle on a well-to-wheel basis. Additionally, a study from Argonne National Laboratory, a research laboratory operated by the University of Chicago for the U.S. Department of Energy, indicates that natural gas vehicles produce at least 13% to 21% fewer greenhouse gas emissions than comparable gasoline and diesel fueled vehicles. 

Safer.    As reported by NGV America, CNG and LNG are relatively safer than gasoline and diesel because they dissipate into the air when spilled or in the event of a vehicle accident. When released, CNG and LNG are also less combustible than gasoline or diesel because they ignite only at relatively high temperatures. The fuel tanks and systems used in natural gas vehicles are subjected to a number of federally required safety tests, such as fire, environmental hazard, burst pressure and crash testing, according to the U.S. Department of Transportation National Highway Traffic Safety Administration. Additionally, CNG and LNG are stored in above-ground tanks and therefore will not contaminate soil or groundwater in the event of a spill or leak.

CNG Sales.    CNG is natural gas that is compressed and dispensed in gaseous form. We typically deliver CNG by obtaining natural gas from local utilities or third-party marketers and then compressing, storing and dispensing it into our customers' vehicles. Some of the natural gas we obtain from third parties for CNG sales is purchased under take-or-pay contracts that require us to purchase minimum volumes of natural gas.

Our subsidiary, NG Advantage also sells CNG for non-vehicle purposes. NG Advantage uses a fleet of 70 high-capacity tube trailers to deliver CNG to institutions and industrial energy users, such as hospitals, food processors, manufacturers and paper mills that do not have direct access to natural gas pipelines. Utilizing its trailer fleet, NG Advantage creates a "virtual natural gas pipeline" that allows oil, diesel or propane users to take advantage of the cost savings and environmental benefits of natural gas. We anticipate that NG Advantage will need to purchase or lease additional trailers in the future to transport CNG in support of its operations.

LNG Production and Sales.    LNG is natural gas that is cooled at a liquefaction facility to approximately -260 degrees Fahrenheit until it condenses into a liquid. We obtain LNG from our own liquefaction plants and from third party suppliers. We own and operate LNG liquefaction plants near Houston, Texas and Boron, California, which we call the "Pickens Plant" and the "Boron Plant," respectively. The Pickens Plant has the capacity to produce 35 million gallons of LNG per year and includes a tanker trailer loading system and a 1.0 million gallon storage tank that can hold up to 840,000 usable gallons. The Boron Plant is capable of producing 60 million gallons of LNG per year and has a dual tanker trailer loading system and a 1.8 million gallon storage tank that can hold up to 1.5 million usable gallons. In 2016, we purchased 44% of our LNG from third-party suppliers and we produced the remainder of our LNG at the Pickens Plant and the Boron Plant. Some natural gas we obtain from third-parties for LNG sales is purchased under “take or pay” contracts that require us to purchase minimum volumes of natural gas.

We sell LNG for use as a vehicle fuel on a bulk basis to fleet customers, who often own and operate their fueling stations, and through our network of public access fueling stations. We deliver LNG via our fleet of 84 tanker trailers to fueling stations, where it is stored and then dispensed in liquid form into vehicles. We contract with third parties to provide tractors and drivers. The need to liquefy and transport LNG generally causes LNG to cost more than CNG. We sell LNG through supply contracts that are priced on an index-plus basis, such that LNG sales under these contracts increase or decrease as a result of an increase or decrease in the cost of natural gas. We also sell LNG vehicle fuel on a per fill-up basis at prices we set at public access stations based on prevailing market conditions. Additionally, we sell LNG for non-vehicle purposes, including to customers who use LNG in oil fields, and for industrial, utility, marine and rail applications.

O&M Services.   We perform O&M services for CNG and LNG fueling stations that we do not own. For these services, we generally charge a fixed or a per-gallon fee based on the volume of fuel dispensed at the station. We have an operations team performing preventive maintenance and available to respond to service requests.

VETC. Under separate pieces of U.S. federal legislation from October 1, 2006 through December 31, 2015, we were eligible to receive a federal alternative fuels tax credit (“VETC”) of $0.50 per gasoline gallon equivalent of CNG and $0.50 per liquid gallon of LNG that we sold as vehicle fuel. From January 1, 2016, the new credit was the same as the credit it replaced, except that the credit for LNG sold as a vehicle fuel in 2016 was based on the diesel gallon equivalent of LNG sold rather than the liquid gallon of LNG sold. Based on the service relationship with our customers, either we or our customers claimed the credit. VETC ceased to be available after it expired on December 31, 2016, and it may not be available for any subsequent period.

Station Construction and Engineering.    We design and construct fueling stations and facility modifications and sell or lease some of these stations to our customers. We charge construction or other fees or lease rates based on the size and complexity of the project.

RNG Production and Sales.    RNG is produced from waste streams such as landfills, animal waste digesters and waste water treatment plants. RNG production plants are connected to natural gas pipelines, which allow RNG to be transported to vehicle fueling stations where it can be compressed and dispensed as CNG, and to LNG liquefaction facilities where it is converted to LNG.

We sell some of the RNG we produce through our natural gas fueling infrastructure for use as a vehicle fuel. In addition, we purchase RNG from third party producers and sell that RNG for vehicle fuel use through our fueling infrastructure. The RNG we sell for vehicle fuel is distributed under the name Redeem™.

Sales of RINs and LCFS Credits.   We generate LCFS Credits when we sell RNG and conventional natural gas for use as a vehicle fuel in California and Oregon, and we generate RIN Credits when we sell RNG for use as a vehicle fuel in the United States. We can sell these credits to third parties who need the RINs and LCFS Credits to comply with federal and state emissions requirements. Generally, the amount of RINs and LCFS Credits we generate increases as we sell higher volumes of natural gas as a vehicle fuel, but the amount of these credits that we sell and our revenue from these sales can vary depending on the market

Natural Gas Fueling Compressors.    Our subsidiary Clean Energy Compression manufactures, sells and services non-lubricated natural gas fueling compressors and related equipment for the global natural gas fueling market. Clean Energy Compression is headquartered near Vancouver, British Columbia, has an additional manufacturing facility near Shanghai, China, and has sales and service offices in the United States, Bangladesh, Colombia and Peru. Clean Energy Compression enables us to satisfy our internal compressor needs since compressors are the most important piece of equipment for a CNG station. Clean Energy Compression also allows us to offer a high-quality and price competitive "equipment only" solution for customers who do not want our full suite of engineering and construction services.

Vehicle Acquisition and Finance.    We offer vehicle finance services, including loans and leases, to help our customers acquire natural gas vehicles. As appropriate, we apply for and receive federal, state and local incentives associated with natural gas vehicle purchases and pass these benefits through to our customers. We may also secure vehicles to place with customers and/or pay deposits with respect to these vehicles prior to receiving a firm order from our customers, which we may be required to purchase if our customers fail to purchase the vehicle as anticipated.

Trucking. We believe that heavy-duty trucking represents one of the greatest opportunities for natural gas to be used as a vehicle fuel in the United States, and as of December 31, 2016 we fuel over 3,000 heavy-duty trucks. Because these high-mileage vehicles consume substantial amounts of fuel, they can derive significant benefits from the lower cost of natural gas. Many well-known shippers, manufacturers, retailers and other truck fleet operators have started to adopt natural gas fueled trucks to move their freight. Such companies include Honda, Frito-Lay, FedEx, Anheuser-Busch, Verizon, Bimbo, Johnson & Johnson, The Home Depot, AT&T, Colgate-Palmolive, Costco Wholesale, Lowes, Pepsi, UPS, MillerCoors, HP, Unilever, Starbucks, Kraft, Kroger, P&G, Hertz and Owens Corning.

Airports. We estimate that vehicles serving airports in the United States, including airport delivery fleets, rental car and parking passenger shuttles and taxis, consume an aggregate of approximately two billion gallons of fuel per year. Additionally, many U.S. airports face emissions challenges and are under regulatory directives and political pressure to reduce pollution, particularly as part of any expansion plans. As a result, many of these airports have adopted various strategies to address tailpipe emissions, including rental car and hotel shuttle consolidation, and requiring or encouraging service vehicle operators to switch their fleets to natural gas. To assist in this effort, airports are contracting with service providers to design, build and operate natural gas fueling stations in strategic locations on their properties.

Refuse. According to INFORM, there are nearly 200,000 refuse trucks in the United States that collect and haul refuse and recyclables, which collectively consume approximately two billion gallons of fuel per year. We estimate that approximately 55% of new refuse trucks in 2016 operate on natural gas, up from approximately 3% of new refuse trucks in 2008. Refuse haulers are increasingly adopting trucks that run on CNG to realize operating savings and to address their customers' demands for reduced emissions.

Transit Agencies. According to the American Public Transportation Association, there are over 71,000 municipal transit buses operating in the United States. In many areas increasingly stringent emissions standards have limited the fueling options available to public transit operators. Also, transit agencies typically fuel at a central location and use high volumes of fuel. We estimate that transit agencies in the United States consume approximately 1.5 billion gallons of fuel per year. Many transit agencies have been early adopters of natural gas vehicles, and over 25% of existing transit buses and over 35% of new transit buses operate on natural gas.

We fuel close to 9,000 transit vehicles and our U.S. public transit customers include the following: Los Angeles Metropolitan Transit Authority, Foothill Transit, Orange County Transit Authority, Santa Monica Big Blue Bus, Dallas Area Rapid Transit Phoenix Transit, Jacksonville Transportation Authority, NICE Bus and Washington Metro Area Transportation Authority. We also serve public transit customers in British Columbia.

Industrial and Institutional Customers. See "Business - Products, Services and Other Business Activities" above for a description of industrial and institutional customers we supply with CNG and LNG.

Government Fleets. In 2014, 2015 and 2016, approximately 18%, 18% and 16% of our revenue, respectively, were derived from contracts with government entities such as municipal transit fleets. As government regulations on pollution continue to become more stringent, government agencies are evaluating ways to make their fleets cleaner and run more economically.

We compete for vehicle fuel users based on demand for the type of fuel, which may be affected by such factors as fuel cost, supply and availability, cost and availability of vehicles, convenience and accessibility of fueling stations, the quality, cleanliness and safety of the fuel, and brand recognition. As of December 31, 2016, we owned, operated or supplied over 570 CNG and LNG fueling stations, which we estimate is approximately four times the number of CNG fueling stations operated by our next largest competitor. We believe we are the only company in the United States or Canada that provides both CNG and LNG vehicle fuel on a significant scale, and our natural gas fueling operations cover more states and provinces than any of our competitors.

CNG and LNG Stations. To construct a CNG or LNG fueling station, we must satisfy permitting and other requirements and either we or a third party contractor must be licensed as a general engineering contractor. Each CNG and LNG fueling station must be constructed in accordance with federal, state and local regulations pertaining to station design, environmental health, accidental release prevention, above-ground storage tanks and hazardous waste and other materials. We are also required to register with certain state agencies as a retailer/wholesaler of CNG and LNG.

Transfer of LNG. Federal safety standards require each transfer of LNG to be conducted in accordance with specific written safety procedures. These procedures must be located at each transfer location and must require that qualified personnel be in attendance during all LNG transfer operations.

LNG Liquefaction Plants. To build and operate LNG liquefaction plants, we must apply for facility permits or licenses that address many factors, including storm water and wastewater discharges, waste handling and air emissions related to production activities or equipment operations. The construction of LNG plants must also be approved by local planning boards and fire departments.

Financing. State agencies generally require the registration of finance lenders. For example, in California, pursuant to the California Finance Lenders Law, one of our subsidiaries is required to be registered as a finance lender with the California Department of Corporations.

Natural Gas Fueling Compressors. Our manufacturing facility for natural gas fueling compressors and other equipment is located in Canada and is registered with the British Columbia Safety Authority and the Society of Mechanical Engineers for manufacturing and operating pressure vessels. Additionally, CNG fueling equipment is manufactured to meet the electrical and mechanical design standards of the country where the equipment will be installed.

RNG. RNG production facilities are required to comply with Title V of the Clean Air Act. In addition, RNG projects must produce RNG that meets the gas quality specifications of the local utilities that accept the gas. These specifications are approved by the applicable state utilities commission.

RIN Credits. In February 2010, the U.S. Environmental Protection Agency ("EPA") finalized the RFS (which was established by the Energy Policy Act of 1992/2005), which creates RINs that can be generated by the production and use of RNG in the transportation sector and can be sold to fuel providers that are not compliant under the RFS.

Greenhouse Gas Emissions. California has adopted laws requiring statewide reductions of greenhouse gas emissions to 1990 levels by 2020, 40% below 1990 levels by 2030, and 80% below 1990 levels by 2050. As of January 1, 2015, California's AB 32 law began regulating the greenhouse gas emissions from transportation fuels, including the emissions associated with LNG and CNG vehicle fuel.

Although our Redeem™ RNG vehicle fuel may qualify for an exemption from AB 32 when sold as LNG or CNG, the availability of any such exemption is uncertain at this time due to the complexity of the requirements that must be met in order to qualify for such an exemption and the possibility of changes to the law. Any Redeem™ volumes that are not exempt would incur compliance costs commensurate with sales of CNG and LNG derived from fossil fuel natural gas.

As of December 31, 2016, we employed 832 people. We have not experienced any work stoppages and none of our employees is subject to collective bargaining agreements. We believe that our employee relations are good.

We operate our business in one reportable segment. For information about our revenue, operating income (loss) and long-lived assets in different geographic areas, see Note 17 to our consolidated financial statements included in this report. We are subject to certain risks attendant to our foreign operations, which are described below in Item 1A. Risk Factors.

In 2014, 2015 and 2016, we incurred pre-tax losses of $89.8 million, $133.8 million and $12.4 million, respectively. During these periods our losses were substantially decreased by approximately $28.4 million, $31.0 million and $26.6 million of revenue, respectively, from the VETC alternative fuels tax credit, which ceased to be available as of January 1, 2017 and may not be available for any subsequent period. We may continue to incur losses, the amount of our losses may increase, and we may never achieve or maintain profitability, which would adversely affect our business, prospects and financial condition, and may cause the price of our common stock to fall.

As of December 31, 2016, our total indebtedness was approximately $314.3 million in principal amount, which includes amounts incurred under the 7.5% Notes, 5.25% Notes, Canton Bonds, and Plains Note, each of which is defined and discussed in Note 10 to our consolidated financial statements included in this report and is reflected under “Contractual Obligations” in Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations of this report. As of December 31, 2016, approximately $6.1 million, $189.6 million, $55.5 million, $54.6 million, $4.0 million and $4.5 million of the principal amount of our indebtedness matures in 2017, 2018, 2019, 2020, 2021 and thereafter, respectively. We expect our total interest payment obligations relating to our indebtedness to be approximately $19.7 million in 2017.

In that case, we may be required to pursue one or more alternatives to meet our debt obligations. For instance, as of the date of this report, we are permitted to repay up to $125.0 million of our outstanding indebtedness at maturity with shares of our common stock rather than cash, with the amount of shares determined by the then-current trading price of our common stock. Any repayment of our debt with equity would increase the number of our outstanding shares and may significantly dilute the ownership interest of our stockholders. Additionally, any shortfall of cash from operations to service our debt may lead us to seek capital from other sources, such as selling assets, restructuring or refinancing our debt or obtaining additional equity capital or debt financing. Our ability to engage in any of these activities, should we decide to do so, would depend on the capital markets, the state of our industry and our business and our financial condition at the time, and we may not be successful in obtaining

As of December 31, 2016, we had total liquidity of $109.8 million consisting of cash and cash equivalents of $36.1 million and short-term investments of $73.7 million. Our business plan calls for approximately $29.0 million in capital expenditures for 2017, as well as additional capital expenditures thereafter. We may also require capital to make principal or interest payments on our indebtedness, either prior to or at their due dates, or for unanticipated expenses, mergers, acquisitions or strategic investments. As a result, we may find it necessary to raise additional capital through selling assets or pursuing debt or equity financing.

In recent years, the prices of oil, gasoline, diesel and natural gas have been volatile, and this volatility may continue. Additionally, prices for crude oil in recent years have been low, due in part to over-production and increased supply without a corresponding increase in demand. Market adoption of CNG, LNG and RNG (which can be delivered in the form of CNG or LNG) as vehicle fuels could be slowed or limited if the low prices and over-supply of gasoline and diesel, today’s most prevalent and conventional vehicle fuels, continue or worsen, or if the price of natural gas increases without equal and corresponding increases in prices of gasoline and diesel. Any of these circumstances could decrease the market's perception of a need for alternative vehicle fuels generally and could cause the success or perceived success of our industry and our business to materially suffer. In addition, low gasoline and diesel prices contribute to the differential between the cost of natural gas vehicles and gasoline or diesel-powered vehicles. Generally, natural gas vehicles cost more initially than gasoline or diesel powered vehicles, as the components needed for a vehicle to use natural gas add to the vehicle’s base cost. Operators seek to recover the additional costs of acquiring or converting to natural gas vehicles over time through the lower costs of fueling natural gas vehicles; however, operators may perceive an inability to timely recover these additional costs if we do not offer CNG and LNG fuel at prices lower than gasoline and diesel. Our ability to offer our customers an attractive pricing advantage for CNG and LNG and maintain an acceptable margin on our sales becomes more difficult if prices of gasoline and diesel decrease or if prices of natural gas increase. These pricing conditions exacerbate the cost differential between natural gas vehicles and gasoline or diesel powered vehicles, which may lead operators to delay or refrain from purchasing or converting to natural gas vehicles at all. Any of these outcomes would decrease our potential customer base and harm our business prospects. Further, fluctuations in natural gas prices affect the cost to us of the natural gas commodity. High natural gas prices adversely impact our operating margins in cases where we cannot pass the increased costs through to our customers. Conversely, lower natural gas prices reduce our revenue in cases where the commodity cost is passed through to our customers. As a result, these fluctuations in natural gas prices can have a significant and adverse impact on our operating results.

We have, and will continue to seek, long-term CNG, LNG and RNG station construction, maintenance and fuel sales contracts with various government bodies, which accounted for approximately 18%, 18% and 16% of our annual revenue in 2014, 2015 and 2016, respectively. In addition to normal business risks, including the other risks discussed in these risk factors, our contracts with government entities are often subject to unique risks, some of which are beyond our control. Long-term government contracts and related orders are subject to cancellation if adequate appropriations for subsequent performance periods are not made. The termination of funding for a government program supporting any of our government contracts could result in a loss of anticipated future revenue attributable to that contract, which could have a negative impact on our operations. The current political climate, including uncertainties following the recent U.S. presidential election, may increase these risks.

We lend to certain qualifying customers a portion and occasionally up to 100% of the purchase price of natural gas vehicles they agree to purchase. Risks associated with these financing activities include, among others, that: the equipment financed consists mostly of vehicles, which are mobile and easily damaged, lost or stolen; and the borrower may default on payments, enter bankruptcy proceedings and/or liquidate. As of December 31, 2016, we had $9.1 million outstanding in loans provided to customers to finance natural gas vehicle purchases.

As a result of the significant fluctuations of our operating results in prior periods, period-to-period comparisons of our operating results may not be meaningful and investors in our common stock should not rely on the results of any one quarter as an indicator of future performance. For example, in the four quarterly periods in 2016, our results were positively affected by gains related to repurchases of our outstanding convertible debt, and such gains may not recur regularly, in the same amounts or at all in future periods. Additionally, if our quarterly results of operations fall below the expectations of securities analysts or investors, the price of our common stock could decline substantially.

As of December 31, 2016, there were 145,538,063 shares of our common stock outstanding, 11,467,796 shares underlying outstanding options, 2,072,304 shares underlying restricted stock units and 16,573,799 shares underlying outstanding convertible notes. All outstanding shares of our common stock are eligible for sale in the public market, subject in certain cases to the requirements of Rule 144 of the Securities Act. Also, shares issued upon exercise or conversion of outstanding options and convertible notes are eligible for sale in the public market to the extent permitted by the provisions of the applicable option and convertible note agreements and Rule 144, or if such shares have been registered under the Securities Act. If these shares are sold, or if it is perceived that they may be sold, in the public market, the trading price of our common stock could decline.

As of December 31, 2016, 12,969,485 shares of our common stock held by our co-founder and board member T. Boone Pickens were pledged as security for loans made to Mr. Pickens. We are not a party to these loans. If the price of our common stock declines, Mr. Pickens may be forced to provide additional collateral for the loans or to sell shares of our common stock in order to remain within the margin limitations imposed under the terms of the loans. Any sales of our common stock following a margin call that is not satisfied or any other large sales of our common stock by our officers and directors, such as Mr. Pickens' sale of 3,000,000 shares of our common stock in December 2016, may cause the price of our common stock to decline.

As of December 31, 2016, our co-founder and board member T. Boone Pickens beneficially owned approximately 11.84% of our outstanding common stock (including 12,969,485 outstanding shares of common stock, 725,000 shares underlying options and 4,113,923 shares underlying convertible promissory notes). As a result, Mr. Pickens is able to influence or control matters requiring approval by our stockholders, including the election of directors and mergers, acquisitions or other extraordinary transactions. Mr. Pickens may have interests that differ from yours and may vote in ways with which you disagree and that may be adverse to your interests. This concentration of ownership may also have the effect of delaying, preventing or deterring a change of control of our Company, which could deprive our stockholders of an opportunity to receive a premium for their stock as part of a sale of our Company and affect the market price of our common stock. Conversely, this concentration may facilitate a change of control at a time when you and other investors may prefer not to sell.

Our corporate headquarters are located at 4675 MacArthur Court, Suite 800, Newport Beach, California 92660, where we occupy approximately 48,000 square feet of office space. Our lease for this facility expires in June 2021.

There were approximately 54 stockholders of record as of March 2, 2017. We believe there are approximately 71,186 additional stockholders whose shares of our common stock are held on their behalf by brokerage firms or other agents.

The following graph compares the five-year total return to holders of our common stock relative to the cumulative total returns of the Nasdaq Global Market Index, and the Russell 2000 Index. The graph assumes that $100 was invested in our common stock and on each of these indices on December 31, 2011 (the last trading day before the beginning of our fifth preceding fiscal year). We chose to include the Russell 2000 Index because it includes issuers with similar market capitalizations as us and due to the lack of a comparable industry or line-of-business index or peer group, as we are the only actively traded public company whose only line of business is to sell natural gas for use as a vehicle fuel and the associated equipment and services necessary to use natural gas as a vehicle fuel.

The consolidated statements of operations data for the years ended December 31, 2014, 2015 and 2016 and the consolidated balance sheet data as of December 31, 2015 and 2016, are derived from our audited consolidated financial statements included in this report. The consolidated statements of operations data for the years ended December 31, 2012 and 2013, and the consolidated balance sheet data as of December 31, 2012, 2013 and 2014 are derived from our audited consolidated financial statements that are not included in this report. Historical results are not indicative of the results to be expected in the current period or any future period.

In evaluating our operating performance, our management focuses primarily on: (1) the amount of CNG, LNG and RNG gasoline gallon equivalents delivered (which we define as (i) the volume of gasoline gallon equivalents we sell to our customers, plus (ii) the volume of gasoline gallon equivalents dispensed at facilities we do not own but where we provide O&M services on a per-gallon or fixed fee basis, plus (iii) our proportionate share of the gasoline gallon equivalents sold as CNG by our joint venture with Mansfield Ventures, LLC called Mansfield Clean Energy Partners, LLC (“MCEP”), plus (iv) our proportionate share (as applicable) of the gasoline gallon equivalents of RNG produced and sold as pipeline quality natural gas by the RNG production facilities we own or operate), (2) our station construction cost of sales, (3) our gross margin (which we define as revenue minus cost of sales), and (4) net income (loss) attributable to us. The following tables, which should be read in conjunction with our consolidated financial statements and notes included in this report, present our key operating data for the years ended December 31, 2014, 2015, and 2016:

RNG Production.   

In November 2016, our subsidiary, Clean Energy Renewables ("Renewables") entered into agreements to form joint ventures with Aria Energy Operating LLC (“Aria”), a developer of RNG production facilities, to develop RNG production facilities at a Republic Services landfill in Oklahoma City, Oklahoma and an Advanced Disposal landfill near Atlanta, Georgia. We refer to these joint ventures as the “RNG Ventures.” Renewables and Aria each have a 50% ownership interest in the RNG Ventures and, subject to certain conditions, are each responsible for 50% of the costs of developing the RNG production facilities that are owned by the RNG Ventures. We also have the exclusive right to purchase 100% of the RNG that will be produced by these facilities for the vehicle fuels market. As of December 31, 2016, we have an investment balance of $0.8 million in the RNG Ventures. See Note 8 to the consolidated financial statements included in this report for further information.

Debt Arrangements.   On February 29, 2016, we entered into a loan and security agreement with, and issued a related promissory note to, PlainsCapital Bank ("Plains"), pursuant to which Plains agreed to lend us up to $50.0 million on a revolving basis for a term of one year (the "Credit Facility"). Simultaneously, we drew down $50.0 million under the Credit Facility, which we repaid in full on August 31, 2016. On October 31, 2016, the Credit Facility's maturity date was extended from February 28, 2017 to September 30, 2018. On December 22, 2016 we drew down $23.5 million under the Credit Facility, which remained outstanding as of December 31, 2016.

See Note 10 to the consolidated financial statements included in this report for further information about our debt.

ATM Program.   On November 11, 2015, we entered into an equity distribution agreement with Citigroup Global Markets Inc. ("Citigroup"), as sales agent and/or principal, to commence an "at-the-market" offering program (the "ATM Program"). Initially, we were permitted to issue and sell, from time to time, through or to Citigroup, shares of our common stock having an aggregate offering price of up to $75.0 million in the ATM Program. On September 9, 2016, we entered into an amended and restated equity distribution agreement with Citigroup for the primary purpose of increasing, from $75.0 million to $110.0 million, the aggregate offering price of shares of our common stock available for issuance and sale in the ATM Program. On December 21, 2016, we entered into a second amended and restated equity distribution agreement with Citigroup for the primary purpose of increasing, from $110.0 million to $200.0 million, the aggregate offering price of shares of our common stock available for issuance and sale in the ATM Program.

VETC Expiration.  On December 31, 2016, the VETC alternative fuels tax credit expired and ceased to be available, and it may not be available in any subsequent period. Under VETC, we were eligible to receive credits of $0.50 per gasoline gallon equivalent of CNG and $0.50 per liquid gallon of LNG that we sold as a vehicle fuel through December 31, 2015, and $0.50 per gasoline gallon equivalent of CNG and $0.50 per diesel gallon equivalent of LNG that we sold as a vehicle fuel from January 1, 2016 through December 31, 2016.

As of December 31, 2016, we had total indebtedness of $314.3 million in principal amount, of which approximately $6.1 million is expected to become due in 2017. Certain of the agreements governing our outstanding debt, which are discussed in Note 10 to our consolidated financial statements included in this report, have certain non-financial covenants with which we must comply. As of December 31, 2016, we were in compliance with all of these covenants.

Market for Natural Gas. CNG and LNG are generally less expensive than gasoline and diesel on an energy equivalent basis and, according to studies conducted by the California Air Resources Board ("CARB") and Argonne National Laboratory, a research laboratory operated by the University of Chicago for the U.S. Department of Energy, cleaner than gasoline and diesel fuel. According to the U.S. Energy Information Administration, demand for natural gas fuels in the United States has increased in recent years and is expected to continue to increase. We believe the growth in demand in recent years is attributable primarily

Our Performance. Our gross revenue is mostly comprised of volume related revenue, compressor and other equipment sales, station construction sales, and VETC revenue. Our revenue can vary between periods due to a variety of factors, including natural gas prices and sale activity, fluctuations in commodity costs and the amount and timing of recognition of government credits, sales of RINs and LCFS credits, compressor and other equipment sales and station construction sales. Our volume-related revenue, which is further discussed below, increased from 2014 to 2016, due largely to the increase in gallons we delivered, and sales of tradable credits in 2015 and 2016.

Volume-Related Revenue. The amount of CNG, LNG and RNG GGEs we delivered increased by 24.1% from 2014 to 2016.

The RNG we sell for vehicle fuel, which is delivered in the form of CNG or LNG is distributed under the name Redeem™. The amount of Redeem vehicle fuel we delivered increased from 20.2 million GGEs in 2014 to 58.6 million GGEs in 2016, a 190.1% increase. We believe this demand for Redeem™ is largely attributable to the lower greenhouse gas emissions that it produces relative to gasoline and diesel.

Our Stations. The number of fueling stations we owned, operated, maintained and/or supplied increased from over 470 as of January 1, 2014 to over 570 as of December 31, 2016 (a 21.3% increase). Included in this number are all of the CNG and LNG fueling stations we own, operate, maintain or with which we have a fueling supply contract.

On a periodic basis we evaluate our estimates based on historical experience and various other assumptions we believe are reasonable under the circumstances. Actual results could differ from those estimates under different assumptions or conditions. For further information on our significant accounting policies, see Note 1 to our consolidated financial statements included in this report.

We are required to use judgment when applying the goodwill impairment test, including, among other considerations, the identification of reporting units and the assessment of qualitative factors involved in the test. Applying this judgment, we have determined that we are a single reporting unit and, based upon our qualitative assessment of goodwill, we have concluded it is more likely than not that the fair value of our reporting unit exceeds its carrying amount and no further quantitative analysis was warranted. During 2014, 2015 and 2016, there were no indicators of impairment to goodwill. Subsequent to December 31, 2016, our stock price has declined due to adverse macroeconomic conditions surrounding the energy industry, which are driven in part by depressed oil prices. As a result of the recent volatility of our market capitalization, it is possible that our goodwill could become impaired, which could result in a material charge and adversely affect our results of operations.

In the fourth quarter of 2014, we determined that a long-lived asset related to a contract acquired in our acquisition of the business of Clean Energy Compression was impaired and recorded an impairment charge of $4.8 million. There were no impairments of our long-lived assets during 2015 and 2016.

See Note 1 to our consolidated financial statements included in this report.

Fiscal Year Ended December 31, 2016 Compared to Fiscal Year Ended December 31, 2015

Revenue.    Revenue increased by $18.4 million to $402.7 million for 2016, from $384.3 million for 2015. This increase was primarily due to increased volumes, including higher RINs and LCFS Credits sales, and increased station construction sales, partially offset by lower VETC revenue and compressor sales.

Volume related revenue increased by $23.3 million between periods primarily due to an increase of 20.5 million gallons delivered, which provided approximately $17.7 million of increased revenue. This increase in gallons delivered was due to a 30.0 million gallon increase in CNG gallons delivered, which was primarily attributable to 16 new refuse customers, six new transit customers and two new trucking customers, partially offset by a 5.8 million decrease in RNG gallons delivered for non-vehicle fuel and a 3.7 million decrease in LNG gallons delivered. Additionally, approximately $5.5 million of the increase in volume related revenue was the result of an increase in the effective price charged per gallon delivered. Our effective price per gallon charged was $0.86 for 2016, a $0.02 per gallon increase from $0.84 per gallon charged for 2015. The increase in our effective price charged was primarily due to increases of $18.7 million and $11.9 million in revenue from sales of RINs and LCFS Credits, respectively, which do not result in increased costs, partially offset by a decline in the effective price per gallon charged of approximately $0.08 per gallon caused primarily by lower retail prices driven by lower commodity costs. The effective price per gallon is defined as revenue generated from selling CNG, LNG, RNG and any related RINs and LCFS Credits and providing O&M services to our vehicle fleet customers at stations that we do not own and for which we receive a per-gallon or fixed fee, all divided by the total GGEs delivered less GGEs delivered by non-consolidated entities, such as entities that are accounted for under the equity method.

Station construction sales increased by $27.1 million between periods, principally from the sale of more full station projects than station upgrades in the 2016 period, as full station projects generally have substantially higher price points than station upgrades.

These revenue increases were partially offset by a decrease in Clean Energy Compression's revenue of $27.2 million between periods due to lower compressor sales, which we believe is a result of a lower global demand for compressors.

VETC revenue decreased by $4.4 million between periods, primarily due to the VETC credit being changed for 2016 to be based on the diesel gallon equivalent of LNG sold rather than the liquid gallon of LNG sold. See “-Overview-Recent Developments-VETC Expiration” above for additional information.

Cost of sales.    Cost of sales decreased by $2.9 million to $255.6 million for 2016, from $258.5 million for 2015. This decrease was primarily due to a $24.1 million decrease in compressor costs between periods, as a result of decreased compressor sales and a $3.5 million decrease in gas commodity costs between periods as a result of a decrease in natural gas prices (discussed below). These decreases were partially offset by a $24.7 million increase in costs related to increased station construction sales between periods.

Our effective cost per gallon decreased by $0.04 per gallon between periods, to $0.52 per gallon for 2016, from $0.56 for 2015. Our effective cost per gallon is defined as the total costs associated with delivering natural gas, including gas commodity costs, transportation fees, liquefaction charges, and other site operating costs, plus the total cost of providing O&M services at stations that we do not own and for which we receive a per-gallon or fixed fee, including direct technician labor, indirect supervisor and management labor, repair parts and other direct maintenance costs, all divided by the total GGEs delivered less GGEs delivered by non-consolidated entities, such as entities that are accounted for under the equity method. The decrease in our effective cost per gallon was primarily due to a decrease in natural gas prices between periods. The decrease in natural gas prices partially offset by the increase in gallons delivered resulted in a net decrease of $3.5 million in gas commodity costs between periods.

Selling, general and administrative.    Selling, general and administrative expenses decreased by $8.2 million to $105.5 million for 2016, from $113.7 million for 2015. This decrease was primarily driven by a $4.9 million decrease in employee-related expenses between periods and a $3.8 million decrease in travel and promotional expenses between periods. These decreases were partially offset by a $0.5 million increase in research and development costs between periods.

Depreciation and amortization.    Depreciation and amortization increased by $4.1 million to $59.3 million for 2016, from $55.2 million for 2015, due to purchases of property and equipment, primarily for our stations.

Gain from extinguishment of debt, net. Gain from extinguishment of debt, net was $34.3 million for 2016 as a result of repurchasing and retiring $284.6 million in principal amount of our 5.25% Notes and SLG Notes, together with $3.6 million accrued and unpaid interest thereon, for an aggregate purchase price of $185.9 million in cash and 20.3 million shares of our common stock. See Note 10 for further information.

Interest expense.    Interest expense decreased by $66.2 million to $29.6 million for 2016, from $95.8 million for 2015. This decrease was primarily due to a non-cash charge of $54.9 million in 2015 related to the elimination of unamortized debt issuance costs associated with our termination of our former credit agreement with General Electric Capital Corporation ("GE"), as well as our reduction of outstanding indebtedness in 2016. See “Overview-Recent Developments-Debt Arrangements” and Note 10 for further information.

Other income (expense), net.    Other income (expense), net, decreased by $(2.9) million to $(0.3) million for 2016, from $2.6 million for 2015. This decrease was primarily due to a $0.8 million increase in the loss from foreign currency transactions not in our subsidiaries’ functional currency, a decrease of $0.5 million between periods as result of a litigation settlement in 2015 and a $1.6 million decrease due to a $0.9 million gain from asset disposals in 2015 compared to $0.7 million in losses from asset disposals in 2016.

Income tax expense.    Income tax expense decreased by $0.3 million to $1.3 million for 2016, from $1.6 million for 2015. The decrease in income tax expense is primarily attributable to a decrease in our tax on foreign operations between periods.

Loss from noncontrolling interest.    In 2016, we recorded a $1.6 million loss for the noncontrolling interest in the net loss of NG Advantage LLC ("NG Advantage"), compared to a $1.2 million loss for 2015. See Note 2 to our consolidated financial statements included in this report for further information. The noncontrolling interest in NG Advantage represents a 46.7% interest, which was held by third parties during the applicable periods.

Fiscal Year Ended December 31, 2015 Compared to Fiscal Year Ended December 31, 2014

Revenue.    Revenue decreased by $44.6 million to $384.3 million for 2015 from $428.9 million for 2014 due to lower effective pricing and fewer station construction and compressor sales. Revenue for station construction sales decreased by $29.6 million principally from the sale of more station upgrades and fewer full station projects in 2015. Full station projects generally have substantially higher price points than station upgrades. Clean Energy Compression revenue decreased by $30.3 million due to the effects of a continued global decline in oil prices, the strength of the U.S. dollar and slower than expected sales in China. Approximately $24.3 million of the decrease in revenue was the result of lower effective prices of gallons delivered, which were caused by lower commodity costs in 2015 compared to 2014. Our effective price per gallon charged was $0.84 for 2015, a $0.10 per gallon decrease from $0.94 per gallon charged for 2014. The decrease in our effective price was due to lower fuel prices driven by lower commodity costs, partially offset by increased RINs and LCFS credits sales of $8.2 and $4.6 million, respectively. The effective price per gallon is defined as revenues generated from selling CNG, LNG, RNG, any related RINs and LCFS Credits sales and providing O&M services to our vehicle fleet customers at stations that we do not own and for which we receive a per-gallon fee, all divided by the total GGEs delivered less GGEs delivered by non-consolidated entities, such as equity method investments.

Cost of sales.    Cost of sales decreased by $50.3 million to $258.5 million for 2015, from $308.8 million for 2014. The decrease was primarily due to fewer station and compressor sales, as we experienced a $24.0 million decrease in station installation costs and a $28.1 million decrease in compressor costs between periods due to decreased activity. Our effective cost per gallon decreased by $0.09 per gallon, from $0.65 per gallon for 2014 to $0.56 per gallon for 2015. Our effective cost per gallon is defined as the total costs associated with delivering natural gas, including gas commodity costs, transportation fees, liquefaction charges, and other site operating costs, plus the total cost of providing O&M services at stations that we do not own and for which we receive a per-gallon fee, including direct technician labor, indirect supervisor and management labor, repair parts and other direct maintenance costs, all divided by the total GGEs delivered less GGEs delivered by non-consolidated entities, such as equity method investments. The decrease in our effective cost per gallon was primarily due to lower natural gas prices. The increased gas volumes delivered partially offset by decreased natural gas prices resulted in a net decrease of $1.2 million in gas commodity costs. In addition, service costs increased as a percentage of service revenues during 2015 due to lower margin services performed by Clean Energy Cryogenics and Clean Energy Compression compared to the prior year.  These decreases were partially offset by a $3.0 million increase between periods of other natural gas delivery costs.

Gain from change in fair value of derivative warrants.    Derivative gains decreased by $4.3 million to $1.4 million for 2015, from $5.7 million for 2014. These amounts represent the non-cash impact with respect to valuing our outstanding warrants based on our mark-to-market accounting for the warrants during the periods (see Note 5 to our consolidated financial statements included in this report).

Selling, general and administrative.    Selling, general and administrative expenses decreased by $12.7 million to $113.7 million for 2015, from $126.4 million for 2014. The decrease is primarily attributable to a $6.7 million decrease in employee-related expenses between periods due to company-wide cost cutting measures. Reduced expenditures in travel and entertainment, stock-based compensation expense, and business insurance premiums led to a decrease of $3.0 million compared to the prior period. Further contributing to the decrease between periods was the absence in 2015 of certain events that caused increased expenses in 2014, such as $1.3 million in retirement benefits related to the retirement of our former Chief Marketing Officer in 2014 and $0.6 million in severance costs related to the departure of our former Chief Financial Officer in 2014.

Impairment of long-lived intangible definite lived assets.    In the fourth quarter of 2014, we recorded an impairment to an intangible asset contract acquired in connection with the Clean Energy Compression acquisition in an amount of $4.8 million. There were no impairments in 2015.

Depreciation and amortization.    Depreciation and amortization increased by $6.1 million to $55.2 million for 2015, from $49.1 million for 2014. This increase was primarily due to additional depreciation expense in 2015 related to increased property and equipment balances between periods from our expanded station network and assets we acquired in our acquisition of NG Advantage during the fourth quarter of 2014.

Interest expense.    Interest expense increased by $51.1 million to $95.8 million for 2015, from $44.7 million for 2014. This increase was primarily due to a non-cash charge related to the elimination of unamortized debt issuance costs of $54.9 million associated with our termination of our Credit Agreement with GE. This increase was partially offset when compared to interest expense 2014 by the extinguishment of the Mavrix Note and resulting discontinuation of interest accrual thereunder in December 2014 (see Note 10 to our consolidated financial statements included in this report for a description of our outstanding debt).

Other income (expense), net.    Other income (expense), net, increased by $5.2 million to $2.6 million for 2015, from $(2.6) million for 2014. This increase was primarily due to foreign currency exchange rate changes between periods on our Clean Energy Compression customer deposits held in foreign currencies and a $1.4 million gain from a litigation settlement in 2015.

Loss from equity method investment.    Losses from our equity method investments increased by $0.3 million to $0.8 million for 2015, compared to a loss of $0.5 million for 2014 due to losses from our MCEP joint venture, which was formed in September 2014.

Gain from sale of subsidiary.    In 2014, we recorded a gain of $12.0 million from the sale of DCE and in 2015 we recorded a related earn-out of $0.9 million (see Note 2 to our consolidated financial statements included in this report for additional discussion of the sale of DCE).

Income tax expense.    Income tax expense increased by $0.5 million to $1.6 million for 2015 compared to $1.1 million for 2014. The increase is primarily attributable to an increase in our tax on foreign operations between periods.

Loss (income) of noncontrolling interest.    In 2015, we recorded $1.2 million for the noncontrolling interest in the net income of NG Advantage and in 2014 we recorded a total of $1.2 million for the noncontrolling interest in the net income of DCE and NG Advantage (see Note 2 to our consolidated financial statements included in this report for additional discussion of the noncontrolling interests in DCE and NG Advantage). The noncontrolling interests represent the 46.7% noncontrolling interest in NG Advantage upon our acquisition of a 53.3% interest in NG Advantage in October 2014, and the 30% interest of our joint venture partner in DCE until September 2014 when we sold 19% of DCE to our joint venture partner, which increased its interest from 30% to 49%. In December 2014, we sold our remaining 51% ownership interest in DCE to the joint venture partner.

Cash provided by operating activities was $46.1 million in 2016, an increase of $58.2 million, compared to $12.1 million used in 2015. The increase in cash provided by operating activities was primarily the result of improved operating results of $36.4 million, exclusive of non-cash expenses and gains, due to an increase in our gross margin and lower interest expense in 2016 compared to 2015. The increase in cash provided by operations was also attributed to a reduction in net working capital of approximately $21.8 million, which resulted primarily from a decrease in other receivables at year end related to the timing of fuel tax credit revenue recognition and cash receipts thereof.

Cash provided by investing activities was $1.1 million in 2016, an increase of $35.0 million compared to $33.9 million used in investing activities in 2015. The increase in cash provided by investing activities was primarily attributable to decreased capital expenditures of $27.8 million between periods, due to cost-cutting efforts and a decrease in construction of Company-owned stations. Additionally, cash provided by our short-term investments that matured, net of purchases, increased by $10.5 million between periods. Partially offsetting this increase in cash provided by investing activities was $0.8 million used in 2016 in connection with the RNG Ventures, which were formed in November 2016 (see Note 8 to the consolidated financial statements) and $1.1 million received in 2015 from the sale of DCE which did not occur again in 2016.

Cash used in financing activities was $55.6 million in 2016 compared to $0.4 million provided by financing activities in 2015. The increase in cash used in financing activities of $56.0 million was primarily due to a $231.5 million increase in debt payments, repayments of long term debt prior to maturity and repayment of our line of credit. Partially offsetting this increase in cash used in financing activities was a $96.4 million increase in cash as a result of our sales of common stock through the ATM

program (as defined and discussed below) and a $80.5 million increase as a result of proceeds from our PlainsCapital Bank credit facility and other debt proceeds.

Our business plan calls for approximately $29.0 million in capital expenditures in 2017, primarily related to the construction of CNG and LNG fueling stations, additional investments in ANGH stations to add CNG fueling, the purchase of additional CNG trailers by NG Advantage and LNG plant maintenance costs.

We had total indebtedness of approximately $314.3 million in principal amount as of December 31, 2016, of which approximately $6.1 million, $189.6 million, $55.5 million, $54.6 million, $4.0 million and $4.5 million is expected to become due in 2017, 2018, 2019, 2020, 2021 and thereafter, respectively. Additionally, we expect our total interest payment obligations relating to our indebtedness to be approximately $19.7 million for the year ending December 31, 2017. We generally intend to make payments under our various debt instruments when due and pursue opportunities for earlier repayment and/or refinancing if and when opportunities arise. With respect to certain of our outstanding indebtedness due in 2018, our board of directors authorized and approved the purchase of our outstanding 5.25% Notes in the open market, in accordance with the terms of the indenture governing the 5.25% Notes and at the date of this report we have used an aggregate $84.3 million for such purchases.

Historically, our principal sources of liquidity have consisted of cash on hand, cash provided by our operations, including, if available, grants, VETC and other credits and cash provided by financing activities and sales of assets. As of December 31, 2016, we had total cash and cash equivalents and short-term investments of $109.8 million, compared to $146.7 million at December 31, 2015.

We commenced the ATM Program on November 11, 2015. We were initially permitted to issue and sell, from time to time, through or to Citigroup, shares of our common stock having an aggregate offering price of up to $75.0 million in the ATM Program. On September 9, 2016 and December 21, 2016, we have increased the aggregate offering price of shares of our common stock available for issuance and sale in the ATM Program, first to $110.0 million and subsequently to $200.0 million. As of the date of this report, shares of our common stock having an aggregate offering price of $78.7 million remain available for sale in the ATM Program. We continue to use any net proceeds from the ATM Program for general corporate purposes, including retiring certain of our indebtedness.

See Note 10 to our consolidated financial statements included in this report for a description of all of our outstanding debt.

The following represents the scheduled maturities of our contractual obligations as of December 31, 2016: