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 March 31, 2010 (except for the Stock Split section of Note 2, as
to which the date is , 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. 5 to Registration
Statement on Form S-1.
CATURANO
AND COMPANY, INC.
Boston, Massachusetts
July 6, 2010
The foregoing consent is in the form that will be signed upon the completion of the stock split
described in Note 2 to the consolidated financial statements.
/s/
Caturano & Company, Inc.
CATURANO
AND COMPANY, INC.
Boston, Massachusetts
July 6, 2010