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Tremisis Energy Acquisition Corporation
EarlyBirdCapital, Inc.
March 3, 2004
Page 4






                                                     March 3, 2004


Tremisis Energy Acquisition Corporation
1775 Broadway
Suite 604
New York, New York 10019

EarlyBirdCapital, Inc.
600 Third Avenue
33rd Floor
New York, New York 10016

                  Re:      Initial Public Offering

Gentlemen:

                  The undersigned stockholder, officer and director of Tremisis
Energy Acquisition Corporation ("Company"), in consideration of
EarlyBirdCapital, Inc. ("EBC") entering into a letter of intent ("Letter of
Intent") to underwrite an initial public offering of the securities of the
Company ("IPO") and embarking on the IPO process, hereby agrees as follows
(certain capitalized terms used herein are defined in paragraph 12 hereof):

                  1. If the Company solicits approval of its stockholders of a
Business Combination, the undersigned will vote all Insider Shares owned by him
in accordance with the majority of the votes cast by the holders of the IPO
Shares.

                  2. In the event that the Company fails to consummate a
Business Combination within 18 months from the effective date ("Effective Date")
of the registration statement relating to the IPO (or 24 months under the
circumstances described in the prospectus relating to the IPO), the undersigned
will take all reasonable actions within his power to cause the Company to
liquidate as soon as reasonably practicable. The undersigned waives any and all
rights he may have to receive any distribution of cash, property or other assets
as a result of such liquidation with respect to his Insider Shares. The
undersigned agrees to indemnify and hold harmless the Company against any and
all loss, liability, claims, damage and expense whatsoever (including, but
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Tremisis Energy Acquisition Corporation
EarlyBirdCapital, Inc.
March 3, 2004
Page 2

not limited to, any and all legal or other expenses reasonably incurred in
investigating, preparing or defending against any litigation, whether pending or
threatened, or any claim whatsoever) which the Company may become subject as a
result of any claim by any vendor or other person who is owed money by the
Company for services rendered or products sold, or by any target business, but
only to the extent necessary to ensure that such loss, liability, claim, damage
or expense does not reduce the amount in the Trust Fund (as defined in the
Letter of Intent).

                  3. In order to minimize potential conflicts of interest which
may arise from multiple affiliations, the undersigned agrees to present to the
Company for its consideration, prior to presentation to any other person or
entity, any suitable opportunity to acquire an operating business, until the
earlier of the consummation by the Company of a Business Combination, the
liquidation of the Company or until such time as the undersigned ceases to be an
officer or director of the Company, subject to any pre-existing fiduciary
obligations the undersigned might have.

                  4. The undersigned acknowledges and agrees that the Company
will not consummate any Business Combination which involves a company which is
affiliated with any of the Insiders unless the Company obtains an opinion from
an independent investment banking firm reasonably acceptable to EBC that the
business combination is fair to the Company's stockholders from a financial
perspective.

                  5. Neither the undersigned, any member of the family of the
undersigned, nor any Affiliate of the undersigned will be entitled to receive
and will not accept any compensation for services rendered to the Company prior
to the consummation of the Business Combination; provided that the undersigned
shall be entitled to reimbursement from the Company for his out-of-pocket
expenses incurred in connection with seeking and consummating a Business
Combination.

                  6. Neither the undersigned, any member of the family of the
undersigned, or any Affiliate of the undersigned will be entitled to receive or
accept a finder's fee or any other compensation in the event the undersigned,
any member of the family of the undersigned or any Affiliate of the undersigned
originates a Business Combination.

                  7. The undersigned will escrow his Insider Shares for the
three year period commencing on the Effective Date subject to the terms of a
Stock Escrow Agreement which the Company will enter into with the undersigned
and American Stock Transfer & Trust Company as escrow agent.
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Tremisis Energy Acquisition Corporation
EarlyBirdCapital, Inc.
March 3, 2004
Page 2


                  8. The undersigned agrees that, during the three year period
terminating on January 27, 2007, he will not become involved (whether as owner,
manager, operator, creditor, partner, shareholder, joint venturer, member,
employee, officer, director, consultant or otherwise) with any Acquisition Fund
(as defined in Section 12(v) below) within the United States, unless such
Acquisition Fund engages EBC to be the managing underwriter of the initial
public offering of the Acquisition Fund's securities.

                     The undersigned hereby agrees and acknowledges that (i) EBC
would be irreparably injured in the event of a breach by the undersigned of any
of his obligations under this paragraph 8, (ii) monetary damages would not be an
adequate remedy for any such breach, and (iii) EBC shall be entitled to
injunctive relief, in addition to any other remedy it may have, in the event of
such breach.

                  9. I agree to be the Chairman of the Board, Chief Executive
Officer and a director of the Company until the earlier of the consummation by
the Copmany of a Business Combination or the liquidation of the Company. The
undersigned's biographical information furnished to the Company and EBC and
attached hereto as Exhibit A is true and accurate in all respects, does not omit
any material information with respect to the undersigned's background and
contains all of the information required to be disclosed pursuant to Section 401
of Regulation S-K, promulgated under the Securities Act of 1933. The
undersigned's Questionnaire furnished to the Company and EBC and annexed as
Exhibit B hereto is true and accurate in all respects. The undersigned
represents and warrants that:

         (a) he is not subject to or a respondent in any legal action for, any
injunction, cease-and-desist order or order or stipulation to desist or refrain
from any act or practice relating to the offering of securities in any
jurisdiction;

         (b) he has never been convicted of or pleaded guilty to any crime (i)
involving any fraud or (ii) relating to any financial transaction or handling of
funds of another person, or (iii) pertaining to any dealings in any securities
and he is not currently a defendant in any such criminal proceeding; and

         (c) he has never been suspended or expelled from membership in any
securities or commodities exchange or association or had a securities or
commodities license or registration denied, suspended or revoked.

                  10. I have full right and power, without violating any
agreement by which I am bound, to enter into this letter agreement and to serve
as Chairman of the
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Tremisis Energy Acquisition Corporation
EarlyBirdCapital, Inc.
March 3, 2004
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Board and Chief Executive Officer of the Company.

                  11. I authorize any employer, financial institution, or
consumer credit reporting agency to release to EBC and its legal representatives
or agents (including any investigative search firm retained by EBC) any
information they may have about my background and finances ("Information").
Neither EBC nor its agents shall be violating my right of privacy in any manner
in requesting and obtaining the Information and I hereby release them from
liability for any damage whatsoever in that connection.

                  12. As used herein, (i) a "Business Combination" shall mean an
acquisition by merger, capital stock exchange, asset or stock acquisition,
reorganization or otherwise, of an operating business selected by the Company;
(ii) "Insiders" shall mean all officers, directors and stockholders of the
Company immediately prior to the IPO; (iii) "Insider Shares" shall mean all of
the shares of Common Stock of the Company owned by an Insider prior to the IPO;
(iv) "IPO Shares" shall mean the shares of Common Stock issued in the Company's
IPO; and (v) "Acquisition Fund" shall mean any company formed with the intent to
offer securities to the public and use the proceeds to consummate one or more
Business Combinations which are unspecified at the time of the securities
offering.

                                  Lawrence S. Coben
                                  ------------------------
                                  Print Name of Insider


                                  /s/ Lawrence S. Coben
                                  ------------------------
                                  Signature


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                                    EXHIBIT A

         LAWRENCE S. COBEN has been our chairman of the board and chief
executive officer since our inception. From January 2001 until December 2003,
Mr. Coben served as senior principal of Sunrise Capital Partners L.P., a private
equity firm established by Houlihan Lokey Howard & Zukin, an international
investment banking firm that invests capital in middle market companies. From
January 1997 to December 2000, Mr. Coben was an independent consultant. From
October 1994 to December 1996, Mr. Coben was chief executive officer of Bolivian
Power Company, Ltd., a New York Stock Exchange-listed company that is Bolivia's
largest private electric generator and distributor until its sale to an
American-Swedish utility consortium. He was also a managing director of Liberty
Power Latin America, L.P., a private developer and owner of power facilities,
from January 1993 to December 1996. He has served as a director of Prisma
Energy, one of the successor Enron companies, since September 2003. Mr. Coben
has also been a director of NRG Energy, Inc. since December 2003, when he was
appointed in connection with its plan of reorganization following its emergence
from Chapter 11 bankruptcy. Mr. Coben is a member of the board of directors of
the Bolivian-American Chamber of Commerce and was the co-chairman of the
Lieberman 2004 National Energy Policy Committee which has devised a plan (the
Declaration of Energy Independence) to reduce American dependence on politically
unstable sources of energy. Mr. Coben is also an archaeologist affiliated with
the University of Pennsylvania and is completing a doctorate in Anthropology.
Mr. Coben received a B.A. in economics from Yale University, an M.A. in
Anthropology (Archaeology) from the University of Pennsylvania and a J.D. from
Harvard School of Law.