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( Mark One ) UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number : 001-34811 Ameresco , Inc. ( Exact name of registrant as specified in its charter ) Delaware ( State or Other Jurisdiction of Incorporation or Organization ) 111 Speen Street , Suite 410 Framingham , Massachusetts ( Address of Principal Executive Offices ) ( 508 ) 661-2200 ( Registrant's Telephone Number , Including Area Code ) Securities registered pursuant to Section 12 ( b ) of the Act : 04-3512838 ( I.R.S. Employer Identification No. ) 01701 ( Zip Code ) Title of each class Class A Common Stock , par value $ 0.0001 per share Trading Symbol AMRC Name of each exchange on which registered New York Stock Exchange No ☐ No ☑ 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 ☑ 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 ☐ 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 ☑ No ☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T during the preceding 12 months ( or for such shorter period that the registrant was required to submit and post such files ) . Yes ☑ No ☐ Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large Accelerated Filer ☐ Emerging growth company ☐ Accelerated Filer ☑ Non - accelerated filer ☐ Smaller reporting company ☐ If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes ☐ No ☑ Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . ☑ The aggregate market value of the voting and non - voting common equity held by non - affiliates computed by reference to the price at which the common equity was last sold on the New York Stock Exchange on June 30 , 2020 , the last business day of the registrant's most recently completed second fiscal quarter , was $ 686,538,169 . Indicate the number of shares outstanding of each of the registrant's classes of common stock as of the latest practicable date . Class Class A Common Stock , $ 0.0001 par value per share Class B Common Stock , $ 0.0001 par value per share Shares outstanding as of February 26 , 2021 30,252,766 18,000,000 DOCUMENTS INCORPORATED BY REFERENCE Portions of the definitive proxy statement for our 2021 annual meeting of stockholders are incorporated by reference into Part III .