Exhibit 4.1

EuroSite Power Inc.
Stock Option Agreement under THE UK SUB-PLAN TO THE
EuroSite Power Inc. 2011 Stock Incentive Plan

EuroSite Power Inc. (the “Company”) hereby grants the following stock option
pursuant to the UK Sub-Plan to the EuroSite Power Inc. 2011 Stock Incentive
Plan. The terms and conditions attached hereto are also a part hereof.

Name of optionee (the “Optionee”):
 
Date of this option grant:
 
Number of shares of the Company’s Common Stock subject to this option
(“Shares”):
 
Option exercise price per Share:
 
Number, if any, of Shares that may be purchased on or after the grant date:
 
Shares that are subject to vesting schedule:
 
Vesting Start Date:
 
Vesting Schedule: 25% of the Shares vest on the Vesting Start Date, and then an
additional 25% of the Shares vest on each of the subsequent three anniversaries
of the Vesting Start Date. In the event of an Acquisition, the Shares will vest
in accordance with Section 2(b).
All vesting is dependent on the continuation of a Business Relationship with the
Company, as provided herein.
The exercise price may be paid by the forms of payment specified in Section
6(a).

This option satisfies in full all commitments that the Company has to the
Optionee with respect to the issuance of stock, stock options or other equity
securities.

EuroSite Power Inc.

By:    _______________________            Signature:    _____________________________
    

Name:         _______________________________
    
Address:    _____________________________

______________________________________

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EUROSITE POWER INC.
Stock Option Agreement

1.    Grant Under Plan. This option is granted pursuant to and is governed by
the UK Sub-Plan to the EuroSite Power Inc. 2011 Stock Incentive Plan (the
“Plan”) and, unless the context otherwise requires, terms used herein shall have
the same meaning as in the Plan.

2.    Vesting of Option.

(a)     Vesting if Business Relationship Continues. The Optionee may exercise
this option on or after the date of this option grant for the number of shares
of Common Stock, if any, set forth on the cover page hereof. If the Optionee has
continuously maintained a Business Relationship (as defined below) with the
Company through the dates listed on the vesting schedule set forth on the cover
page hereof, the Optionee may exercise this option for the additional number of
shares of Common Stock set opposite the applicable vesting date. Notwithstanding
the foregoing, the Board may, in its discretion, accelerate the date that any
installment of this option becomes exercisable. The foregoing rights are
cumulative and may be exercised only before the date which is ten years from the
date of this option grant.

(b)  Accelerated Vesting Due to Acquisition. In the event an Acquisition that is
not a Private Transaction occurs while the Optionee maintains a Business
Relationship with the Company and this option has not fully vested, this option
shall become exercisable for 100% of the then number of Shares as to which it
has not vested, such vesting to occur immediately prior to the closing of the
Acquisition.

(c) Definitions. The following definitions shall apply:

“Acquisition” means (i) the sale of the Company by merger in which the
shareholders of the Company in their capacity as such no longer own a majority
of the outstanding equity securities of the Company (or its successor); or (ii)
any sale of all or substantially all of the assets or capital stock of the
Company (other than in a spin-off or similar transaction) or (iii) any other
acquisition of the business of the Company, as determined by the Board.

“Business Relationship” means service to the Company or its successor in the
capacity of an employee.

“Private Transaction” means any Acquisition where the consideration received or
retained by the holders of the then outstanding capital stock of the Company
does not consist of (i) cash or cash equivalent consideration, (ii) securities
which are registered under the Securities the Securities Act of 1933, as
amended, or any successor statute (the “Securities Act”) and/or (iii) securities
for which the Company or any other issuer thereof has agreed, including pursuant
to a demand, to file a registration statement within ninety (90) days of
completion of the transaction for resale to the public pursuant to the
Securities Act.

“Data” shall mean certain personal information about the Optionee, including,
but not limited to, name, home address and telephone number, date of birth,
social insurance number, salary, nationality, job title, any stock, units or
directorships held in the Company, details of all options or other entitlement
to shares awarded, cancelled, exercised, vested, unvested, or outstanding in the
Optionee's favour.

“Data Recipients” shall mean third parties assisting the Company in the
implementation, administration, and management of the Plan.

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“ITEPA” shall mean the Income Tax (Earnings and Pensions) Act 2003.

“Joint Election” shall mean an election (in such terms and such form as provided
in paragraphs 3A and 3B of Schedule 1 to the Social Security Contributions and
Benefits Act 1992), which has been approved by HM Revenue & Customs for the
transfer of the whole or any liability of the secondary contributor for any
Secondary NIC Liability.

“Option Tax Liability” shall mean any liability or obligation of the Company
and/or any related company or Subsidiary to account for income tax (under Pay As
You Earn) or any other taxation provisions and primary class 1 National
Insurance Contributions in the United Kingdom to the extent arising from the
grant, exercise, assignment, release, cancellation or any other disposal of an
Option or arising out of the acquisition, retention and disposal of the Shares
acquired under this Plan.

“Personal Representative” shall mean the personal representative(s) of an
Optionee (being either the executors of his will or if he dies intestate the
duly appointed administrator(s) of his estate) who have provided to the Board
evidence of their appointment as such.

“Secondary NIC Liability” shall mean any liability to employer's Class 1
National Insurance Contributions to the extent arising from the grant, exercise,
release or cancellation of an Option or arising out of the acquisition,
retention and disposal of the Shares acquired pursuant to an Option.

“Section 431 Election” shall mean an election made under section 431 of the
Income Tax (Earnings and Pensions) Act 2003.

“Taxable Event” shall mean any occasion on which an Option Tax Liability or
Secondary NIC Liability arises in connection with an Option or any award of
Common Stock under it.

“UK Subsidiary” shall mean a Subsidiary of the Company which is incorporated in
the UK.

“Unapproved Option” shall mean an option over shares in the Company that is
neither an HM Revenue & Customs approved Company Share Option Plan nor an
Enterprise Management Incentive Option.

3.    Termination of Business Relationship.

(a)    Termination. If the Optionee’s Business Relationship with the Company
ceases, voluntarily or involuntarily, no further installments of this option
shall become exercisable, and this option shall expire (may no longer be
exercised) after the passage of 30 days from the date of termination, but in no
event later than the scheduled expiration date. Any determination under this
agreement as to the status of a Business Relationship or other matters referred
to above shall be made in good faith by the Board.

(b)     Employment Status. For purposes hereof, with respect to employees of the
Company, employment shall not be considered as having terminated during any
leave of absence if such leave of absence has been approved in writing by the
Company and if such written approval contractually obligates the Company to
continue the employment of the Optionee after the approved period of absence; in
the event of such an approved leave of absence, vesting of this option shall be
suspended (and the period of the leave of absence shall be added to all vesting
dates) unless otherwise provided in the Company’s written approval of the leave
of absence. For purposes hereof, a termination of employment followed by another
Business Relationship shall be deemed a termination of the Business Relationship
with all vesting to cease unless the Company enters into a written agreement
related to such other Business Relationship in which it is specifically stated
that there is no termination of the Business Relationship under this agreement.
This option shall not be affected by any

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change of employment within or among the Company and its Subsidiaries so long as
the Optionee continuously remains an employee of the Company or any Subsidiary.

4.    Death; Disability.

(a)    Death. Upon the death of the Optionee while the Optionee is maintaining a
Business Relationship with the Company, this option may be exercised, to the
extent otherwise exercisable on the date of the Optionee’s death, by the
Optionee’s Personal Representative only at any time within 12 months after the
date of death, but not later than the scheduled expiration date.

(b)    Disability. If the Optionee ceases to maintain a Business Relationship
with the Company by reason of his or her disability, this option may be
exercised, to the extent otherwise exercisable on the date of cessation of the
Business Relationship, only at any time within 12 months after such cessation of
the Business Relationship, but not later than the scheduled expiration date. For
purposes hereof, “disability” means “permanent and total disability” as defined
in Section 22(e) (3) of the Code.

5.    Partial Exercise. This option may be exercised in part at any time and
from time to time within the above limits, except that this option may not be
exercised for a fraction of a share.

6.    Payment of Exercise Price.

(a)     Payment Options. The exercise price (together with any Option Tax
Liability and Secondary NIC Liability) shall be paid by one or any combination
of the following forms of payment that are applicable to this option, as
indicated on the cover page hereof:

(i)
by cheque payable to the order of the Company; or

(ii)
provided that the Company’s Common Stock is then listed on a securities
exchange, including the Nasdaq Global Market, or on the Over-the-Counter
Bulletin Board, by delivery of an irrevocable and unconditional undertaking,
satisfactory in form and substance to the Company, by a creditworthy broker to
deliver promptly to the Company sufficient funds to pay the exercise price, or
delivery by the Optionee to the Company of a copy of irrevocable and
unconditional instructions, satisfactory in form and substance to the Company,
to a creditworthy broker to deliver promptly to the Company cash or a cheque
sufficient to pay the exercise price.

7.    Securities Laws Restrictions on Resale. Until registered under the
Securities Act, the Shares will be illiquid and will be deemed to be “restricted
securities” for purposes of the Securities Act. Accordingly, such shares must be
sold in compliance with the registration requirements of the Securities Act or
an exemption therefrom and may need to be held indefinitely. Unless the Shares
have been registered under the Securities Act, each certificate evidencing any
of the Shares shall bear a restrictive legend specified by the Company.

8.    Method of Exercising Option. Subject to the terms and conditions of this
agreement, this option may be exercised by written notice to the Company at its
principal executive office, or to such transfer agent as the Company shall
designate. Such notice shall state the election to exercise this option and the
number of Shares for which it is being exercised and shall be signed by the
person or persons so exercising this option. Such notice shall be accompanied by
payment of the full purchase price of such shares (together with any Option Tax
Liability and Secondary NIC Liability), a signed Joint Election, and a signed
Section 431 Election, and the Company shall deliver a certificate or
certificates representing such shares as soon as practicable after the notice
shall be received. Such certificate or certificates shall be registered in the
name of the person or persons so exercising this option. In the event this
option shall be exercised, pursuant to Section 5 hereof, by any person or
persons other than the Optionee, such notice shall be accompanied by appropriate
proof of the right of such person or persons to exercise this option.

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9.    Option Not Transferable. This option is not transferable or assignable
except to the Optionee’s Personal Representative on death of the Optionee.
During the Optionee’s lifetime only the Optionee can exercise this option.

10.    No Obligation to Exercise Option. The grant and acceptance of this option
imposes no obligation on the Optionee to exercise it.

11.    No Obligation to Continue Business Relationship. Neither the Plan, this
agreement, nor the grant of this option imposes any obligation on the Company to
continue the Optionee in employment or other Business Relationship.

12.    Adjustments. Except as is expressly provided in the Plan with respect to
certain changes in the capitalization of the Company, no adjustment shall be
made for dividends or similar rights for which the record date is prior to such
date of exercise.

13.    Tax Obligations.

(a)
Withholding. In the event that the Company determines that it is required to
account to HM Revenue & Customs for the Option Tax Liability and any Secondary
NIC Liability or to withhold any other tax as a result of the exercise of this
option, the Optionee, as a condition to the exercise of this option, shall make
arrangements satisfactory to the Company to enable it to satisfy all withholding
liabilities. The Optionee shall also make arrangements satisfactory to the
Company to enable it to satisfy any withholding requirements that may arise in
connection with the vesting or disposition of Shares purchased by exercising
this option.

(b)
Tax Consultation. The Optionee understands that he or she may suffer adverse tax
consequences as a result of Optionee’s purchase or disposition of the Shares.
The Optionee represents that he or she will consult with any tax advisors the
Optionee deems appropriate in connection with the purchase or disposition of the
Shares and that the Optionee is not relying on the Company for any tax advice.

(c)
Section 431 Election. As a further condition of the exercise of this Option, the
Optionee shall have signed a Section 431 election under Section 431 ITEPA in the
form set out in the Appendix or in such other form as may be determined by HM
Revenue & Customs from time to time.

(d)
Employer's National Insurance Charges. As a further condition of the exercise of
an Option under this Plan the Optionee shall join with the Company, or if and to
the extent that there is a change in the law, any other company or person who is
or becomes a Secondary Contributor in making a Joint Election which has been
approved by HM Revenue & Customs, for the transfer of the whole of any liability
of any Secondary NIC Liability.

(e)
Optionee's Tax Indemnity.

(i)
Indemnity. To the extent permitted by law, the Optionee hereby agrees to
indemnify and keep indemnified the Company, and the Company as trustee for and
on behalf of any related corporation, for any Option Tax Liability.

(ii)
No Obligation to Issue Shares. The Company shall not be obliged to allot and
issue any Shares or any interest in Shares pursuant to the exercise of this
option unless and until the Optionee has paid to the Company such sum as is, in
the opinion of the Company, sufficient to indemnify the Company in full against
the Option Tax Liability and the Secondary NIC Liability, or the Optionee has
made such other arrangement as in the opinion of the Company will ensure that
the full amount of any Option Tax Liability and any Secondary NIC Liability will
be recovered from the Optionee within such period as the Company may then
determine.

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(iii)
Right of Retention. In the absence of any such other arrangement being made, the
Company shall have the right to retain out of the aggregate number of shares to
which the Optionee would have otherwise been entitled upon the exercise of this
option, such number of Shares as, in the opinion of the Company, will enable the
Company to sell as agent for the Optionee (at the best price which can
reasonably expect to be obtained at the time of the sale) and to pay over to the
Company sufficient monies out of the net proceeds of sale, after deduction of
all fees, commissions and expenses incurred in relation to such sale, to satisfy
the Optionee's liability under such indemnity.

14.    Data Protection. By entering into this Option Agreement, and as a
condition of the grant of the Option, the Optionee consents to the collection,
use, and transfer of personal data as described in this paragraph to the full
extent permitted by and in full compliance with applicable laws.

(a)
The Optionee understands that the Company and its Subsidiaries hold certain
personal information about the Optionee for the purpose of managing and
administering the Plan.

(b)
The Optionee further understands that the Company and/or its Subsidiaries will
transfer Data among themselves as necessary for the purposes of implementation,
administration, and management of the Optionee’s participation in the Plan, and
that the Company and/or its Subsidiary may each further transfer Data to any
Data Recipients.

(c)
The Optionee understands that these Data Recipients may be located in the
Optionee’s country of residence or elsewhere, such as the United States. the
Optionee authorises the Data Recipients to receive, possess, use, retain, and
transfer Data in electronic or other form, for the purposes of implementing,
administering, and managing the Optionee’s participation in the Plan, including
any transfer of such Data, as may be required for the administration of the Plan
and/or the subsequent holding of Shares on the Optionee’s behalf, to a broker or
third party with whom the Shares acquired on exercise may be deposited. Where
the transfer is to be to a destination outside the European Economic Area, the
Company shall take reasonable steps to ensure that the Optionee's personal data
continues to be adequately protected and securely held.

(d)
The Optionee understands that the Optionee may, at any time, review the Data,
request that any necessary amendments be made to it, or withdraw the Optionee's
consent herein in writing by contacting the Company. The Optionee further
understands that withdrawing consent may affect the Optionee's ability to
participate in the Plan.

1.
Additional terms.

(a)
Optionee has no right to compensation or damages for any loss in respect of the
Option where such loss arises (or is claimed to arise), in whole or in part,
from the termination of Optionee's employment; or notice to terminate employment
given by or to Optionee. This exclusion of liability shall apply however
termination of employment, or the giving of notice, is caused other than in a
case where a competent tribunal or court, from which there can be no appeal (or
which the relevant employing company has decided not to appeal), has found that
the cessation of the Optionee’s employment amounted to unfair or constructive
dismissal of Optionee and however compensation or damages may be claimed.

(b)
The Optionee has no right to compensation or damages for any loss in respect of
an Option where such loss arises (or is claimed to arise), in whole or in part,
from any company ceasing to be a member of the group of companies of which the
Company is the parent; or the transfer of any business from a company which is a
member of that group to any person which is not a member of that group. This
exclusion of liability shall apply however the change of status of the relevant
company, or the transfer of the relevant business, is caused, and however
compensation or damages may be claimed. Optionee has no right to compensation or
damages for any loss in respect of an Option where such loss arises (or is
claimed to

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arise), in whole or in part, from any company ceasing to be a Subsidiary of the
Company; or the transfer of any business from a Subsidiary of the Company to any
person which is not a Subsidiary of the Company. This exclusion of liability
shall apply however the change of status of the relevant company, or the
transfer of the relevant business, is caused, and however compensation or
damages may be claimed.

16.    Arbitration. Any dispute, controversy, or claim arising out of, in
connection with, or relating to the performance of this agreement or its
termination shall be settled by arbitration in Boston, Massachusetts, pursuant
to the rules then obtaining of the American Arbitration Association. Any award
shall be final, binding and conclusive upon the parties and a judgment rendered
thereon may be entered in any court having jurisdiction thereof.

17.    Provision of Documentation to Optionee. By signing this agreement the
Optionee acknowledges receipt of a copy of this agreement and a copy of the
Plan.

18.    Miscellaneous.

(a)    Notices. All notices hereunder shall be in writing and shall be deemed
given when sent by mail, if to the Optionee, to the address shown on the records
of the Company, and if to the Company, to the Company’s principal executive
offices, attention of the Corporate Secretary.

(b)    Entire Agreement; Modification. This agreement constitutes the entire
agreement between the parties relative to the subject matter hereof, and
supersedes all proposals, written or oral, and all other communications between
the parties relating to the subject matter of this agreement. This agreement may
be modified, amended or rescinded only by a written agreement executed by both
parties.

(c)     Fractional Shares. If this option becomes exercisable for a fraction of
a share because of the adjustment provisions contained in the Plan, such
fraction shall be rounded down.

(d)    Issuances of Securities; Changes in Capital Structure. Except as
expressly provided herein or in the Plan, no issuance by the Company of shares
of stock of any class, or securities convertible into shares of stock of any
class, shall affect, and no adjustment by reason thereof shall be made with
respect to, the number or price of shares subject to this option. No adjustments
need be made for dividends paid in cash or in property other than securities of
the Company. If there shall be any change in the Common Stock of the Company
through merger, consolidation, reorganization, recapitalization, stock dividend,
stock split, combination or exchange of shares, spin-off, split-up or other
similar change in capitalization or event, the restrictions contained in this
agreement shall apply with equal force to additional and/or substitute
securities, if any, received by the Optionee in exchange for, or by virtue of
his or her ownership of, Shares, except as otherwise determined by the Board.

(e)    Severability. The invalidity, illegality or unenforceability of any
provision of this agreement shall in no way affect the validity, legality or
enforceability of any other provision.

(f)    Successors and Assigns. This agreement shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and assigns,
subject to the limitations set forth in Section 10 hereof.

(g)    Governing Law. This agreement shall be governed by and interpreted in
accordance with the laws of the State of Delaware, without giving effect to the
principles of the conflicts of laws thereof. The Joint Election and Section 431
Election shall be governed by the laws of England and Wales.

This Agreement has been executed and delivered as a deed on the date set out
below.

Dated:                

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SIGNED as a DEED
BY EUROSITE POWER, INC    )
acting by the under-mentioned        )
person(s) acting on the authority of    )
the Company in accordance with the    )
laws of the territory of its incorporation:    )

By: ___________________

SIGNED as a DEED    

By:    ____________________    

Name:     ____________________

in the presence of:
Witness signature:     ________________________

Name:            ________________________

Address:         ________________________

Occupation:        ___________________

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