Exhibit 10.3

REGISTRATION RIGHTS AGREEMENT

THIS REGISTRATION RIGHTS AGREEMENT is made as of the 14th day of June, 2013, by
and among EuroSite Power Inc., a Delaware corporation (the “Company”), and each
of the holders of the Company’s 4% Senior Convertible Notes due 2015 (the
“Notes”) listed on Schedule A hereto, each of which is referred to in this
Agreement as a “Noteholder”. The parties hereby agree as follows:

1.Definitions. For purposes of this Agreement:

1.1    “Affiliate” means, with respect to any specified Person, any other Person
directly or indirectly controlling or controlled by or under direct or indirect
common control with such specified Person. For the purposes of this definition,
“control”, when used with respect to any Person, means the power to direct the
management and policies of such Person, directly or indirectly, whether through
the ownership of voting securities, by contract or otherwise; and the terms
“controlling” and “controlled” have meanings correlative to the foregoing.

1.2    “Common Stock” means shares of the Company’s common stock, par value
$0.001 per share.

1.3    “Company” has the meaning given such term in the first paragraph of this
Agreement.

1.4    “Damages” means any loss, damage, claim or liability (joint or several)
to which a party hereto may become subject under the Securities Act, the
Exchange Act, or other federal or state law, insofar as such loss, damage, claim
or liability (or any action in respect thereof) arises out of or is based upon
(i) any untrue statement or alleged untrue statement of a material fact
contained in any registration statement of the Company, including any
preliminary prospectus or final prospectus contained therein or any amendments
or supplements thereto; (ii) an omission or alleged omission to state therein a
material fact required to be stated therein, or necessary to make the statements
therein not misleading; or (iii) any violation or alleged violation by the
indemnifying party (or any of its agents or Affiliates) of the Securities Act,
the Exchange Act, any state securities law, or any rule or regulation
promulgated under the Securities Act, the Exchange Act, or any state securities
law.

1.5    “Demand Notice” has the meaning given such term in Subsection 2.1.

1.6    “Exchange Act” means the Securities Exchange Act of 1934, as amended, and
the rules and regulations promulgated thereunder.

1.7    “Form S 3” means such form under the Securities Act as in effect on the
date hereof or any registration form under the Securities Act subsequently
adopted by the SEC that permits incorporation of substantial information by
reference to other documents filed by the Company with the SEC.

1.8    “Holder” means any holder of Registrable Securities who is a party to
this Agreement.

1.9    “Initiating Holders” means, collectively, Holders who properly initiate a
registration request under this Agreement.

1.10    “Noteholders” has the meaning given such term in the first paragraph of
this Agreement.

1.11    “Noteholders Agreement” means the Noteholders Agreement, dated as of the
date hereof, among the Company and the initial Noteholders.

1.12    “Notes” has the meaning given such term in the first paragraph of this
Agreement.

1.13    “Person” means any individual, corporation, partnership, limited
liability company, joint venture, association, joint-stock company, trust,
unincorporated organization, government or any agency or political subdivision
thereof or any other entity.

1.14    “Registrable Securities” means the Common Stock issuable or issued upon
conversion of the Notes pursuant to the terms of the Noteholders Agreement,
excluding for purposes of Section 2 any shares for which registration rights
have terminated pursuant to Subsection 2.8 of this Agreement.

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1.15    “SEC” means the Securities and Exchange Commission.

1.16    “Securities Act” means the Securities Act of 1933, as amended, and the
rules and regulations promulgated thereunder.

1.17    “Selling Holder Counsel” has the meaning given such term in Subsection
2.5.

1.18    “Selling Expenses” means all underwriting discounts, selling
commissions, and stock transfer taxes applicable to the sale of Registrable
Securities, and fees and disbursements of counsel for any Holder, except for the
fees and disbursements of the Selling Holder Counsel borne and paid by the
Company as provided in Subsection 2.5.

2.Registration Rights. The Company covenants and agrees as follows:

2.1    Demand Registration.

(a)    If at any time when the Company is eligible to use a Form S-3
registration statement, the Company receives, prior to the first anniversary of
this Agreement, a request from Holders of at least thirty percent (30%) of the
Registrable Securities that the Company file a Form S-3 registration statement
with respect to outstanding Registrable Securities of such Holders having an
anticipated aggregate offering price, net of Selling Expenses, of at least
$250,000, then the Company shall (i) within ten (10) days after the date such
request is given, give notice thereof (the “Demand Notice”) to all Holders other
than the Initiating Holders; and (ii) as soon as practicable, and in any event
within thirty (30) days after the date such request is given by the Initiating
Holders, file a Form S-3 registration statement under the Securities Act
covering all Registrable Securities requested to be included in such
registration by any other Holders, as specified by notice given by each such
Holder to the Company within twenty (20) days of the date the Demand Notice is
given, and in each case, subject to the limitations of Subsection 2.1(b) and
Subsection 2.2.

(b)    Notwithstanding the foregoing obligations, if the Company furnishes to
Holders requesting a registration pursuant to this Subsection 2.1 a certificate
signed by the Company’s chief executive officer stating that in the good faith
judgment of the Company’s Board of Directors it would be materially detrimental
to the Company and its stockholders for such registration statement to be filed
and it is therefore necessary to defer the filing of such registration
statement, then the Company shall have the right to defer taking action with
respect to such filing, and any time periods with respect to filing or
effectiveness thereof shall be tolled correspondingly, for a period of not more
than sixty (60) days after the request of the Initiating Holders is given;
provided, however, that the Company may not invoke this right more than twice.

(c)    The Company shall not be obligated to effect, or to take any action to
effect, any registration pursuant to Subsection 2.1(a) (i) during the period
that is thirty (30) days before the Company’s good faith estimate of the date of
filing of, and ending on a date that is thirty (30) days after the effective
date of, a Company-initiated registration for a firm commitment underwriting,
provided, that the Company is actively employing in good faith commercially
reasonable efforts to cause such registration statement to become effective; or
(ii) if the Company has effected a registration pursuant to Subsection 2.1(a)
within the twelve (12) month period immediately preceding the date of such
request. A registration shall not be counted as “effected” for purposes of this
Subsection 2.1(c) until such time as the applicable registration statement has
been declared effective by the SEC, unless the Initiating Holders withdraw their
request for such registration, elect not to pay the registration expenses
therefor, and forfeit their right to one demand registration statement pursuant
to Subsection 2.5, in which case such withdrawn registration statement shall be
counted as “effected” for purposes of this Subsection 2.1(c).

2.2    Underwriting Requirements. If, pursuant to Subsection 2.1, the Initiating
Holders intend to distribute the Registrable Securities covered by their request
by means of an underwriting, they shall so advise the Company as a part of their
request made pursuant to Subsection 2.1, and the Company shall include such
information in the Demand Notice. The underwriter(s) will be selected by the
Company and shall be reasonably acceptable to a majority in interest of the
Initiating Holders. In such event, the right of any Holder to include such
Holder’s Registrable Securities in such registration shall be conditioned upon
such Holder’s participation in such underwriting and the inclusion of such
Holder’s Registrable Securities in the underwriting to the extent provided
herein. All Holders proposing to distribute their securities through such
underwriting shall (together with the Company as provided in Subsection 2.3(e))
enter into an underwriting agreement in customary form with the underwriter(s)
selected for such underwriting. Notwithstanding any other provision of this
Subsection 2.2, if the underwriter(s) advise(s) the Initiating Holders in
writing that marketing factors require a limitation on the number of shares to
be underwritten, then the Initiating Holders shall so advise all Holders of
Registrable Securities that otherwise would be underwritten pursuant hereto, and
the number of Registrable Securities that may be included in the underwriting
shall be allocated among such Holders of Registrable Securities, including the
Initiating Holders, in proportion (as nearly as practicable) to the number of
Registrable Securities owned by each Holder or in such other proportion as shall
mutually be

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agreed to by all such selling Holders; provided, however, that the number of
Registrable Securities held by the Holders to be included in such underwriting
shall not be reduced unless all other securities are first entirely excluded
from the underwriting. To facilitate the allocation of shares in accordance with
the above provisions, the Company or the underwriters may round the number of
shares allocated to any Holder to the nearest 100 shares.

2.3    Obligations of the Company. Whenever required under this Section 2 to
effect the registration of any Registrable Securities, the Company shall, as
expeditiously as reasonably possible:

(a)    prepare and file with the SEC a registration statement with respect to
such Registrable Securities and use its commercially reasonable efforts to cause
such registration statement to become effective and, upon the request of the
Holders of a majority of the Registrable Securities registered thereunder, keep
such registration statement effective until the earlier of the distribution
contemplated in the registration statement has been completed or until such time
as all of the Registrable Securities covered by such registration statement may
be resold without restriction under the Securities Act;

(b)    prepare and file with the SEC such amendments and supplements to such
registration statement, and the prospectus used in connection with such
registration statement, as may be necessary to comply with the Securities Act in
order to enable the disposition of all securities covered by such registration
statement;

(c)    furnish to the selling Holders such numbers of copies of a prospectus,
including a preliminary prospectus, as required by the Securities Act, and such
other documents as the Holders may reasonably request in order to facilitate
their disposition of their Registrable Securities;

(d)    use its commercially reasonable efforts to register and qualify the
securities covered by such registration statement under such other securities or
blue-sky laws of such jurisdictions as shall be reasonably requested by the
selling Holders; provided that the Company shall not be required to qualify to
do business or to file a general consent to service of process in any such
states or jurisdictions, unless the Company is already subject to service in
such jurisdiction and except as may be required by the Securities Act;

(e)    in the event of any underwritten public offering, enter into and perform
its obligations under an underwriting agreement, in usual and customary form,
with the underwriter(s) of such offering;

(f)    use its commercially reasonable efforts to cause all such Registrable
Securities covered by such registration statement to be listed on a national
securities exchange or trading system and each securities exchange and trading
system (if any) on which similar securities issued by the Company are then
listed;

(g)    provide a transfer agent and registrar for all Registrable Securities
registered pursuant to this Agreement and provide a CUSIP number for all such
Registrable Securities, in each case not later than the effective date of such
registration;

(h)    promptly make available for inspection by the selling Holders, any
underwriter(s) participating in any disposition pursuant to such registration
statement, and any attorney or accountant or other agent retained by any such
underwriter or selected by the selling Holders, all financial and other records,
pertinent corporate documents, and properties of the Company, and cause the
Company’s officers, directors, employees, and independent accountants to supply
all information reasonably requested by any such seller, underwriter, attorney,
accountant, or agent, in each case, as necessary or advisable to verify the
accuracy of the information in such registration statement and to conduct
appropriate due diligence in connection therewith;

(i)    notify each selling Holder, promptly after the Company receives notice
thereof, of the time when such registration statement has been declared
effective or a supplement to any prospectus forming a part of such registration
statement has been filed; and

(j)    after such registration statement becomes effective, notify each selling
Holder of any request by the SEC that the Company amend or supplement such
registration statement or prospectus.

2.4    Furnish Information. It shall be a condition precedent to the obligations
of the Company to take any action pursuant to this Section 2 with respect to the
Registrable Securities of any selling Holder that such Holder shall furnish to
the Company such information regarding itself, the Registrable Securities held
by it, and the intended method of disposition of such securities as is
reasonably required to effect the registration of such Holder’s Registrable
Securities.

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2.5    Expenses of Registration. All expenses (other than Selling Expenses)
incurred in connection with registrations, filings, or qualifications pursuant
to Section 2, including all registration, filing, and qualification fees;
printers’ and accounting fees; fees and disbursements of counsel for the
Company; and the reasonable fees and disbursements of one counsel for the
selling Holders (“Selling Holder Counsel”), shall be borne and paid by the
Company; provided, however, that the Company shall not be required to pay for
any expenses of any registration proceeding begun pursuant to Subsection 2.1 if
the registration request is subsequently withdrawn at the request of the Holders
of a majority of the Registrable Securities to be registered (in which case all
selling Holders shall bear such expenses pro rata based upon the number of
Registrable Securities that were to be included in the withdrawn registration),
unless the Holders of a majority of the Registrable Securities agree to forfeit
their right to one registration pursuant to Subsection 2.1. All Selling Expenses
relating to Registrable Securities registered pursuant to this Section 2 shall
be borne and paid by the Holders pro rata on the basis of the number of
Registrable Securities registered on their behalf.

2.6    Delay of Registration. No Holder shall have any right to obtain or seek
an injunction restraining or otherwise delaying any registration pursuant to
this Agreement as the result of any controversy that might arise with respect to
the interpretation or implementation of this Section 2.

2.7    Indemnification. If any Registrable Securities are included in a
registration statement under this Section 2:

(a)    To the extent permitted by law, the Company will indemnify and hold
harmless each selling Holder, and the partners, members, officers, directors,
and stockholders of each such Holder; legal counsel and accountants for each
such Holder; any underwriter (as defined in the Securities Act) for each such
Holder; and each Person, if any, who controls such Holder or underwriter within
the meaning of the Securities Act or the Exchange Act, against any Damages, and
the Company will pay to each such Holder, underwriter, controlling Person, or
other aforementioned Person any legal or other expenses reasonably incurred
thereby in connection with investigating or defending any claim or proceeding
from which Damages may result, as such expenses are incurred; provided, however,
that the indemnity agreement contained in this Subsection 2.7(a) shall not apply
to amounts paid in settlement of any such claim or proceeding if such settlement
is effected without the consent of the Company, which consent shall not be
unreasonably withheld, nor shall the Company be liable for any Damages to the
extent that they arise out of or are based upon actions or omissions made in
reliance upon and in conformity with written information furnished by or on
behalf of any such Holder, underwriter, controlling Person, or other
aforementioned Person expressly for use in connection with such registration.

(b)    To the extent permitted by law, each selling Holder, severally and not
jointly, will indemnify and hold harmless the Company, and each of its
directors, each of its officers who has signed the registration statement, each
Person (if any), who controls the Company within the meaning of the Securities
Act, legal counsel and accountants for the Company, any underwriter (as defined
in the Securities Act), any other Holder selling securities in such registration
statement, and any controlling Person of any such underwriter or other Holder,
against any Damages, in each case only to the extent that such Damages arise out
of or are based upon actions or omissions made in reliance upon and in
conformity with written information furnished by or on behalf of such selling
Holder expressly for use in connection with such registration; and each such
selling Holder will pay to the Company and each other aforementioned Person any
legal or other expenses reasonably incurred thereby in connection with
investigating or defending any claim or proceeding from which Damages may
result, as such expenses are incurred; provided, however, that the indemnity
agreement contained in this Subsection 2.7(b) shall not apply to amounts paid in
settlement of any such claim or proceeding if such settlement is effected
without the consent of the Holder, which consent shall not be unreasonably
withheld; and provided further that in no event shall the aggregate amounts
payable by any Holder by way of indemnity or contribution under Subsections
2.7(b) and 2.7(d) exceed the proceeds from the offering received by such Holder
(net of any Selling Expenses paid by such Holder), except in the case of fraud
or willful misconduct by such Holder.

(c)    Promptly after receipt by an indemnified party under this Subsection 2.7
of notice of the commencement of any action (including any governmental action)
for which a party may be entitled to indemnification hereunder, such indemnified
party will, if a claim in respect thereof is to be made against any indemnifying
party under this Subsection 2.7, give the indemnifying party notice of the
commencement thereof. The indemnifying party shall have the right to participate
in such action and, to the extent the indemnifying party so desires, participate
jointly with any other indemnifying party to which notice has been given, and to
assume the defense thereof with counsel mutually satisfactory to the parties;
provided, however, that an indemnified party (together with all other
indemnified parties that may be represented without conflict by one counsel)
shall have the right to retain one separate counsel, with the fees and expenses
to be paid by the indemnifying party, if representation of such indemnified
party by the counsel retained by the indemnifying party would be inappropriate
due to actual or potential differing interests between such indemnified party
and any other party represented by

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such counsel in such action.

(d)    To provide for just and equitable contribution to joint liability under
the Securities Act in any case in which either (i) any party otherwise entitled
to indemnification hereunder makes a claim for indemnification pursuant to this
Subsection 2.7 but it is judicially determined (by the entry of a final judgment
or decree by a court of competent jurisdiction and the expiration of time to
appeal or the denial of the last right of appeal) that such indemnification may
not be enforced in such case, notwithstanding the fact that this Subsection 2.7
provides for indemnification in such case, or (ii) contribution under the
Securities Act may be required on the part of any party hereto for which
indemnification is provided under this Subsection 2.7, then, and in each such
case, such parties will contribute to the aggregate losses, claims, damages,
liabilities, or expenses to which they may be subject (after contribution from
others) in such proportion as is appropriate to reflect the relative fault of
each of the indemnifying party and the indemnified party in connection with the
statements, omissions, or other actions that resulted in such loss, claim,
damage, liability, or expense, as well as to reflect any other relevant
equitable considerations. The relative fault of the indemnifying party and of
the indemnified party shall be determined by reference to, among other things,
whether the untrue or allegedly untrue statement of a material fact, or the
omission or alleged omission of a material fact, relates to information supplied
by the indemnifying party or by the indemnified party and the parties’ relative
intent, knowledge, access to information, and opportunity to correct or prevent
such statement or omission; provided, however, that, in any such case, (x) no
Holder will be required to contribute any amount in excess of the public
offering price of all such Registrable Securities offered and sold by such
Holder pursuant to such registration statement, and (y) no Person guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the
Securities Act) will be entitled to contribution from any Person who was not
guilty of such fraudulent misrepresentation; and provided further that in no
event shall a Holder’s liability pursuant to this Subsection 2.7(d), when
combined with the amounts paid or payable by such Holder pursuant to Subsection
2.7(b), exceed the proceeds from the offering received by such Holder (net of
any Selling Expenses paid by such Holder), except in the case of willful
misconduct or fraud by such Holder.

(e)    Unless otherwise superseded by an underwriting agreement entered into in
connection with the underwritten public offering, the obligations of the Company
and Holders under this Subsection 2.7 shall survive the completion of any
offering of Registrable Securities in a registration under this Section 2, and
otherwise shall survive the termination of this Agreement.

2.8    Termination of Registration Rights. The right of any Holder to request
registration or inclusion of Registrable Securities in any registration pursuant
to Subsection 2.1 shall terminate upon such time as all of such Holder’s
Registrable Securities may be resold without restriction under the Securities
Act; and

3.Miscellaneous.

3.1    Successors and Assigns. This Agreement shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and permitted
assigns.

3.2    Governing Law and Venue. This Agreement shall be governed by, and
construed in accordance with, the laws of the State of New York and, to the
extent it involves any United States statute or regulations, in accordance
therewith. The parties hereby consent and submit to the exclusive jurisdiction
of the state and federal courts in New York City with respect to all disputes
arising in connection with this Agreement.

3.3    Counterparts. This Agreement may be executed in two or more counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument. Counterparts may be delivered via
facsimile, electronic mail (including pdf) or other transmission method and any
counterpart so delivered shall be deemed to have been duly and validly delivered
and be valid and effective for all purposes.

3.4    Titles and Subtitles. The titles and subtitles used in this Agreement are
for convenience only and are not to be considered in construing or interpreting
this Agreement.

3.5    Notices. Any demand, authorization notice, request, consent or
communication shall be given in writing and shall be deemed effectively given:
(i) upon personal delivery to the party to be notified, (ii) when sent by
confirmed electronic mail or facsimile if sent during normal business hours of
the recipient, and if not so confirmed, then on the next business day, (iii)
five days after having been sent by registered or certified mail (or regular
mail if registered or certified mail is unavailable in the country of the
recipient), (iv) if sent within the U.S., one business day after deposit with a
recognized overnight courier, specifying next business day delivery, with
written verification of receipt or (v) if sent from the U.S. to an address
outside the U.S. or if sent from outside the U.S. to an address within the U.S.,
five business days after deposit with an internationally recognized courier
service if, specifying that delivery be made within five business days with
written

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verification of receipt. All notices and other communications shall be sent if
sent to a Holder, to the address, fax number or email address of such Holder set
forth on the signature page to this Agreement, as it may subsequently change on
the Company’s books by notice from the Holder; and

If to the Company, to:        EuroSite Power Inc.
45 First Street
Waltham, MA 02451
Attention: Chief Financial Officer
Fax No.: (781) 622-1027
Phone No.: (781) 622-1117

With a copy to:            Sullivan & Worcester LLP
One Post Office Square
Boston, MA 02109
Attention: Edwin L. Miller, Jr.
Fax No.: (617) 338-2880
Phone No.: (617) 338-2800

Such notices or communications shall be effective when received. If a notice or
communication to a Holder is sent in the manner provided above, it is duly
given, whether or not the addressee receives it.

The Company by notice to the Holders may designate additional or different
addresses for subsequent notices or communications.

Failure to mail a notice or communication to a Holder or any defect in it shall
not affect its sufficiency with respect to other Holders.

3.6    Amendments and Waivers. Any term of this Agreement may be amended and the
observance of any term of this Agreement may be waived (either generally or in a
particular instance, and either retroactively or prospectively) only with the
written consent of the Company and the Holders of a majority of the Registrable
Securities; and provided further that any provision hereof may be waived by any
waiving party on such party’s own behalf, without the consent of any other
party. Notwithstanding the foregoing, this Agreement may not be amended or
terminated and the observance of any term hereof may not be waived with respect
to any Holder without the written consent of such Holder, unless such amendment,
termination, or waiver applies to all Holders in the same fashion. The Company
shall give prompt notice of any amendment or termination hereof or waiver
hereunder to any party hereto that did not consent in writing to such amendment,
termination, or waiver. Any amendment, termination, or waiver effected in
accordance with this Subsection 3.6 shall be binding on all parties hereto,
regardless of whether any such party has consented thereto. No waivers of or
exceptions to any term, condition, or provision of this Agreement, in any one or
more instances, shall be deemed to be or construed as a further or continuing
waiver of any such term, condition, or provision.

3.7    Severability. In case any one or more of the provisions contained in this
Agreement is for any reason held to be invalid, illegal or unenforceable in any
respect, such invalidity, illegality, or unenforceability shall not affect any
other provision of this Agreement, and such invalid, illegal, or unenforceable
provision shall be reformed and construed so that it will be valid, legal, and
enforceable to the maximum extent permitted by law.

3.8    Aggregation of Stock. All shares of Registrable Securities held or
acquired by Affiliates shall be aggregated together for the purpose of
determining the availability of any rights under this Agreement and such
Affiliated Persons may apportion such rights as among themselves in any manner
they deem appropriate.

3.9    Entire Agreement. This Agreement (including any Schedules and Exhibits
hereto) constitutes the full and entire understanding and agreement among the
parties with respect to the subject matter hereof, and any other written or oral
agreement relating to the subject matter hereof existing between the parties is
expressly canceled.

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IN WITNESS WHEREOF, the parties have executed this Agreement as of the date
first written above.

EUROSITE POWER INC.

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

Counterpart signature pages attached

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