X0202 SCHEDULE 13G 0001125725 XXXXXXXX LIVE Class A Common Stock 08/20/2026 0001488139 Ameresco, Inc. 02361E108 111 Speen Street Framingham MA 01701 Rule 13d-1(c) Gagnon Securities LLC b DE 0.00 951125.00 0.00 999794.00 999794.00 N 2.9 BD IA Gagnon Advisors, LLC b DE 0.00 472798.00 0.00 472798.00 472798.00 N 1.3 IA Neil Gagnon b X1 153541.00 1551948.00 153541.00 1609325.00 1762866.00 N 5.0 IN Ameresco, Inc. 111 Speen Street, Framingham, Massachusetts 01701 Neil Gagnon has sole voting and dispositive power over 153,541 shares of the Issuer's Class A Common Stock (the "Common Stock"). In addition, Mr. Gagnon has shared voting power over 1,551,948 shares of Common Stock and shared dispositive power over 1,609,325 shares of Common Stock. Mr. Gagnon is the Chief Executive Officer and principal owner of Gagnon Securities LLC ("GS"), an investment adviser registered with the U.S. Securities and Exchange Commission ("SEC") under the Investment Advisers Act of 1940, as amended (the "Advisers Act"), and a registered broker-dealer, in its role as investment manager to several customer accounts, foundations, partnerships and trusts (collectively, the "Accounts") to which it furnishes investment advice. GS and Mr. Gagnon may be deemed to share voting power with respect to 951,125 shares of Common Stock held in the Accounts and dispositive power with respect to 999,794 shares of Common Stock held in the Accounts. GS and Mr. Gagnon expressly disclaim beneficial ownership of all securities held in the Accounts. Mr. Gagnon is also the managing member of Gagnon Advisors, LLC ("Gagnon Advisors"), an investment adviser registered with the SEC under the Advisers Act. Mr. Gagnon and Gagnon Advisors, in its role as investment manager to Gagnon Investment Associates, LLC ("GIA"), a private investment fund, may be deemed to share voting and dispositive power with respect to the 472,798 shares of Common Stock held by GIA. Gagnon Advisors and Mr. Gagnon expressly disclaim beneficial ownership of all securities held by GIA. 1370 Ave. of Americas, 26th Floor, New York, NY 10019 Gagnon Securities LLC Delaware limited liability company Gagnon Advisors, LLC Delaware limited liability company Neil Gagnon USA Y Gagnon Securities LLC 999,794 Gagnon Advisors, LLC 472,798 Neil Gagnon 1,762,866 Gagnon Securities LLC 2.9% Gagnon Advisors, LLC 1.3% Neil Gagnon 5.0% Calculation of percentage of beneficial ownership is based on 35,066,211 Common Stock outstanding as of July 31, 2026, based on the Issuer's Form 10-Q filed with the Securities and Exchange Commission on August 4, 2026. Gagnon Securities LLC 0 Gagnon Advisors, LLC 0 Neil Gagnon 153,541 Gagnon Securities LLC 951,125 Gagnon Advisors, LLC 472,798 Neil Gagnon 1,551,948 Gagnon Securities LLC 0 Gagnon Advisors, LLC 0 Neil Gagnon 153,541 Gagnon Securities LLC 999,794 Gagnon Advisors, LLC 472,798 Neil Gagnon 1,609,325 Y N The Accounts described above in Item 2 have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, securities held in their respective accounts. To the knowledge of the Reporting Persons, the interest in any such account does not exceed 5% of the class of securities. Except to the extent described herein, the Reporting Person disclaims beneficial ownership of all such securities. Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. Gagnon Securities LLC /s/ Neil Gagnon 08/27/2026 Gagnon Advisors, LLC /s/ Neil Gagnon 08/27/2026 Neil Gagnon /s/ Neil Gagnon 08/27/2026