In connection with its special meeting of stockholder scheduled
for May 18, 2017 to consider its merger with Tecogen, Inc. (the
“Special Meeting”), on April 28, 2017, Tecogen Inc (the
“Company”), issued a press release announcing the commencement of
mailing a notice of meeting, a definitive proxy statement and a
proxy card to each of its stockholders (the Mailing). The Special
Meeting is scheduled to be held on May 18, 2017, at 11 a.m.,
Eastern Time, at the Companys principal executive offices at 45
First Avenue, Waltham, Massachusetts 02451, to consider and vote
on a proposal to approve the issuance of the shares of common
stock, par value $.001 per share, of the Company to the Agreement
and Plan of Merger, dated as of November 1, 2016, as subsequently
amended (the Merger Agreement), among the Company, Tecogen.ADGE
Acquisition Corp., a Delaware corporation and a wholly-owned
subsidiary of the Company (Merger Sub), and American DG Energy
Inc. (ADGE), to which Merger Sub will merge with and into ADGE,
with ADGE as the surviving entity such that ADGE will become a
wholly-owned subsidiary of the Company (the Merger). Stockholders
of record of the Company at the close of business on April 24,
2017, will be entitled to vote by proxy or in person at the
Special Meeting.

Completion of the Merger is subject to certain conditions,
including approval by the Companys stockholders and other
customary closing conditions.

A copy of the press release is furnished as Exhibit 99.1 hereto
and incorporated herein by reference.

CAUTIONARY NOTE REGARDING FORWARD LOOKING STATEMENTS

This Current Report on Form 8-K, or this Current Report, contains
forward looking statements within the meaning of the Private
Securities Litigation Reform Act of 1995 and other securities
laws. The forward looking statements are subject to various known
and unknown risks, uncertainties and other factors. When the
Company uses words such as believes, expects, anticipates,
estimates, plans or similar expressions, the Company is making
forward looking statements. Although the Company believes that
its forward-looking statements are based on reasonable
assumptions, its expected results may not be achieved, and actual
results may differ materially from its expectations. For example,
this Current Report states the date that the Company expects to
mail the proxy statement to its stockholders and the date of the
Special Meeting. These dates could change and the mailing and/or
the date of the Special Meeting could be delayed.

You should not rely upon forward-looking statements except as
statements of the Companys present intentions and of the Companys
present expectations, which may or may not occur. You should read
these cautionary statements as being applicable to all
forward-looking statements wherever they appear. Except as
required by law, the Company undertakes no obligation to release
publicly the result of any revision to these forward-looking
statements that may be made to reflect events or circumstances
after the date hereof or to reflect the occurrence of
unanticipated events. Readers are also urged to carefully review
and consider the various disclosures the Company has made in this
document as well as the Companys other filings with the SEC,
including the sections captioned Risk Factors and Cautionary Note
Regarding Forward Looking Statements in the Companys Annual
Report on Form 10-K for the year ended December 31, 2016 filed
with the SEC on March 23, 2017.

Additional Information

This Current Report may be deemed to be solicitation material in
respect of the proposed stockholder vote approving the Merger.
The Company has filed with the SEC a Registration Statement on
Form S-4, which Registration Statement will include a definitive
proxy statement of the Company, a definitive proxy statement of
ADGE and prospectus of the Company (when available). The
Registration Statement was declared effective by the SEC on April
12, 2017. The Mailing was mailed on or about April 27, 2017, to
stockholders of the Company as of April 24, 2017. BEFORE MAKING
ANY VOTING DECISION, THE COMPANYS STOCKHOLDERS ARE URGED TO READ
ALL RELEVANT DOCUMENTS FILED WITH THE SEC, INCLUDING, WHEN
AVAILABLE, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, BECAUSE
THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE MERGER.
Stockholders will be able to obtain, without charge, a copy of
the definitive proxy statement/prospectus (when available) and
other documents that the Company and ADGE file with the SEC from
the SECs website at www.sec.gov.

The Company, ADGE, their respective directors and executive
officers and certain other members of their management and
employees may be deemed to be participants in the solicitation of
proxies in connection with the Special Meeting at which the
Companys stockholders will have the opportunity to vote on the
proposed Merger. Additional information regarding the interests
of such potential participants will be included or incorporated
by reference in the definitive proxy statement/prospectus (when
available).

Item 9.01 Financial Statements and Exhibits

(d) Exhibits

The following exhibit relating to Item 8.01 shall be deemed to be
furnished, and not filed: