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                                          June 18, 2002

Environmental Power Corporation
One Cate Street, 4/th/ Floor
Portsmouth, New Hampshire 03801

Re:  Registration Statement on Form S-2 (File No. 333-85332)

Ladies and Gentlemen:

   We have acted as counsel to Environmental Power Corporation, a Delaware
corporation (the "Company"), in connection with the Registration Statement on
Form S-2 (the "Registration Statement") filed by the Company under the
Securities Act of 1933, as amended (the "Act"), relating to the registration of
an aggregate 16,632,315 shares of the Company's common stock (the "Common
Stock"), consisting of: (i) 15,694,183 outstanding shares of Common Stock (the
"Outstanding Shares"), (ii) 821,170 shares of Common Stock issuable upon the
exercise of warrants (the "Warrants"), and (iii) 116,962 shares of Common Stock
issuable upon the exercise of options (the "Options").

   As such counsel, we have participated in the preparation of the Registration
Statement and have examined originals or copies, certified or otherwise
identified to our satisfaction, of such documents, corporate records,
certificates of public officials and other instruments and have conducted such
other investigations of fact and law as we have deemed relevant and necessary
to form a basis for the opinions hereinafter expressed. In conducting such
examination, we have assumed (i) that all signatures are genuine, (ii) that all
documents and instruments submitted to us as copies conform with the originals,
and (iii) the due execution and delivery of all documents where due execution
and delivery are a prerequisite to the effectiveness thereof. As to any facts
material to this opinion, we have relied upon statements and representations of
officers and other representatives of the Company and certificates of public
officials and have not independently verified such facts.

   Based solely upon the foregoing, it is our opinion that: The Outstanding
Shares to be sold by the shareholders as described in the Registration
Statement have been validly issued and are fully paid and non-assessable. The
shares of Common Stock issuable upon the exercise of the Warrants and the
Options have been duly authorized and reserved and, when issued in accordance
with the respective terms of the Warrants and the Options against payment
therefore, will be validly issued, fully paid and non-assessable.

   Our opinion expressed above is limited to the laws of the General
Corporation Law of the State of Delaware and the federal laws of the United
States of America.

   We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement, and to the reference to our firm under the heading
"Legal Matters" in the Prospectus constituting part of the Registration
Statement relating to the registration of the Shares. In giving such consent,
we do not thereby admit that we are in the category of persons whose consent is
required under Section 7 of the Act.

                                          Very truly yours,


                                          /s/ Dorsey & Whitney LLP



