Exhibit 23.1
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
As independent registered public accountants, we hereby consent to the use of the report of
Caturano & Company, Inc. dated July 20, 2010 relating to the financial statements of
Ameresco, Inc. and Subsidiaries as of December 31, 2009 and December 31, 2008 and for the three
years ended December 31, 2009 (which report expresses an unqualified opinion) included in, and to
all references to our Firm included in or made a part of, this
Amendment No. 6 to Registration
Statement on Form S-1.
/s/
Caturano & Company, Inc.
CATURANO
AND COMPANY, INC.
Boston, Massachusetts
July 20, 2010