Exhibit 10.4

THIS NOTE AND ANY COMMON STOCK ISSUABLE UPON THE CONVERSION OF THIS NOTE OR AS
PAYMENT OF INTEREST ON THIS NOTE HAVE NOT BEEN REGISTERED UNDER THE U.S.
SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND MAY NOT BE SOLD
OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR ANY APPLICABLE
EXEMPTION THEREFROM.
THIS NOTE AND ANY COMMON STOCK ISSUABLE UPON THE CONVERSION OF THIS NOTE OR AS
PAYMENT OF INTEREST ON THIS NOTE MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE
TRANSFERRED UNLESS (I) A REGISTRATION STATEMENT FOR THE SECURITIES UNDER THE
SECURITIES ACT IS IN EFFECT, (II) THE CORPORATION HAS RECEIVED AN OPINION OF
COUNSEL, WHICH OPINION IS SATISFACTORY TO THE CORPORATION, TO THE EFFECT THAT
SUCH REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT OR (III) SUCH OFFER
OR TRANSFER IS MADE IN ACCORDANCE WITH THE PROVISIONS OF REGULATION S UNDER THE
SECURITIES ACT. HEDGING TRANSACTIONS INVOLVING THESE SECURITIES MAY NOT BE
CONDUCTED UNLESS IN COMPLIANCE WITH THE SECURITIES ACT.
THE HOLDER OF THIS SECURITY IS ENTITLED TO THE BENEFITS OF A NOTEHOLDERS
AGREEMENT AND A REGISTRATION RIGHTS AGREEMENT AND, BY ITS ACCEPTANCE HEREOF,
AGREES TO BE BOUND BY AND TO COMPLY WITH THE PROVISIONS OF SUCH AGREEMENTS.
EUROSITE POWER INC.

4% SENIOR CONVERTIBLE NOTE DUE 2015

EuroSite Power Inc., a Delaware corporation (the “Company”, which term shall
include any successor corporation under the Noteholders Agreement referred to
below), promises to pay to American DG Energy Inc., or registered assigns, the
principal sum of One Million, One Hundred Thousand Dollars ($1,100,000) on June
14, 2015. The Company promises to pay interest on the principal amount of this
Note at the rate of 4.00% per annum. The first interest payment date on this
Note is December 14, 2013, and thereafter, the Company shall pay interest
semi-annually in arrears on June 14 and December 14 of each calendar year and at
maturity, whether by acceleration or otherwise.  Interest on the Notes shall
accrue from the most recent date to which interest has been paid or, if no
interest has been paid, from June 14, 2013.  Interest will be computed on the
basis of a 360-day year of twelve 30-day months.
This Note is one of a duly authorized issue of Notes of the Company designated
as its 4% Senior Convertible Notes due 2015 (the “Notes”), issued under a
Noteholders Agreement, dated as of June 14, 2013 (together with any exhibits and
schedules thereto and as such may be amended from time to time, the “Noteholders
Agreement”), between the Company and the initial Holders. The Holder of this
Note is entitled to the benefits thereof and is subject to the provisions
thereof.
IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed.
Attest:                            EUROSITE POWER INC.

By: /s/ Anthony S. Loumidis                By: /s/ Barry J. Sanders
Name: Anthony S. Loumidis                Name: Barry J. Sanders
Title: Chief Financial Officer                Title: Chief Executive Officer

Dated: June 14, 2013    

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GUARANTEE
For value received, American DG Energy Inc., a corporation organized under the
laws of the State of Delaware (herein called the “Guarantor,” which term
includes any successor corporation under the Noteholders Agreement referred to
in the Note upon which this Guarantee is endorsed), hereby unconditionally
guarantees to the Holder of the Note upon which this Guarantee is endorsed the
due and punctual payment of the principal of, and interest on, such Note, any
other amount due and payable pursuant to the terms of the Noteholders Agreement
when and as the same shall become due and payable, whether at the Stated
Maturity, by declaration of acceleration, repayment at the option of the Holder
or otherwise, according to the terms thereof and of the Noteholders Agreement.
In case of the failure of the Company punctually to make any such payment of
principal or interest, the Guarantor hereby agrees to cause any such payment to
be made punctually when and as the same shall become due and payable, whether at
the Stated Maturity or by declaration of acceleration, or otherwise, and as if
such payment were made by the Company.
Capitalized terms used herein and not otherwise defined shall have the meanings
ascribed to such terms in the Noteholders Agreement.
The Guarantor hereby agrees that its obligations hereunder shall be as if it
were principal debtor and not merely surety, and shall be absolute and
unconditional (except as to the specific subordination provisions contained in
Section 6.8 of the Noteholders Agreement), irrespective of, and shall be
unaffected by, any invalidity, subordination, irregularity or unenforceability
of such Note or such Noteholders Agreement, any failure to enforce the
provisions of such Note or such Noteholders Agreement, or any waiver,
modification or indulgence granted to the Company with respect thereto, by the
Holder of such Note or the Trustee or any other circumstance which may otherwise
constitute a legal or equitable discharge of a surety or guarantor. The
Guarantor hereby waives the benefits of diligence, presentment, demand of
payment, filing of claims with a court in the event of merger, insolvency or
bankruptcy of the Company, any right to require a proceeding first against the
Company, protest or notice with respect to such Note or the indebtedness
evidenced thereby and all demands whatsoever, and covenants that this Guarantee
will not be discharged except by strict and complete performance of the
obligations contained in such Note and this Guarantee. The Guarantor hereby
agrees that, in the event of a default in payment of principal of, and interest
on, such Note, the Holders of the Notes, on the terms and conditions set forth
in the Noteholders Agreement, may proceed directly against the Guarantor to
enforce this Guarantee without first proceeding against the Company.
The Guarantor shall be subrogated to all rights of the Holder of such Note
against the Company in respect of any amounts paid to such Holder by the
Guarantor on account of such Note pursuant to the provisions of this Guarantee
or the Noteholders Agreement; provided, however, that the Guarantor shall not be
entitled to enforce, or to receive any payments arising out of or based upon,
such right of subrogation until the principal of, and interest on, on all Notes
issued under such Noteholders Agreement shall have been paid in full.
Claims under this Guarantee are, to the extent provided in the Noteholders
Agreement, subject in right of payment to the prior payment in full of all
Senior Guarantor Indebtedness, and this Guarantee is issued subject to the
provisions of the Noteholders Agreement with respect thereto. Each Holder of a
Note upon which this Guarantee is endorsed, by accepting the same, agrees to and
shall be bound by such provisions.
No reference herein to such Noteholders Agreement and no provision of this
Guarantee or of such Noteholders Agreement shall alter or impair the guarantee
of the Guarantor, which is absolute and unconditional (except as to the specific
subordination provisions contained in Section 6.8 of the Noteholders Agreement),
of the due and punctual payment of principal and interest on the Note upon which
this Guarantee is endorsed.
All terms used in this Guarantee which are defined in such Noteholders Agreement
shall have the meanings assigned to them in such Noteholders Agreement.This
Guarantee shall be deemed to be a contract made under the laws of the State of
New York, and for all purposes shall be governed by and construed in accordance
with the laws of the State of New York.
IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly executed
under its corporate seal and dated the date on the face hereof.
AMERICAN DG ENERGY INC.

By: /s/ Anthony S. Loumidis
Name: Anthony S. Loumidis
Title: Chief Financial Officer

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ASSIGNMENT FORM
I or we assign and transfer this Note to:
                                                
(Assignee's name, address and zip code)     (Assignee's soc. sec. or tax I.D.
no.)
Date:                                            
(Sign exactly as your name appears on the other side of this Note)

*Signature guaranteed by:    
By:                

* Signature to be guaranteed in a manner satisfactory to the Company.

CONVERSION NOTICE
To convert this Note into Common Stock of the Company, check the box:
To convert only part of this Note, state the principal amount to be converted
(must be $1,000 or an integral multiple of $1,000): $ ___________________.
If you want the stock certificate made out in another person's name, fill in the
form below:
I or we assign and transfer this Note to:
                                                
(Assignee's name, address and zip code)    (Assignee's soc. sec. or tax I.D.
no.)
Date:                                            
(Sign exactly as your name appears on the other side of this Note)
*Signature guaranteed by:    
By:                

* Signature to be guaranteed in a manner satisfactory to the Company.

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