Exhibit 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT

TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report on Form 10-Q of Ameresco, Inc. (the “Company”) to which this certification is attached and as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned officers of the Company hereby certifies, pursuant to Rule 13a-14(b) and 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1)	The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and
(2)	The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.
Date: August 8, 2019		/s/ George P. Sakellaris
		George P. Sakellaris
		President and Chief Executive Officer (principal executive officer)
Date: August 8, 2019		/s/ Mark Chiplock
		Mark Chiplock
		Vice President, Corporate Controller and Chief Accounting Officer (duly authorized and principal financial officer, through July 29, 2019)
Date: August 8, 2019		/s/ Spencer Doran Hole
		Spencer Doran Hole
		Senior Vice President and Chief Financial Officer (duly authorized and principal financial officer, effective July 29, 2019)