Document:

Exhibit 4.4

 

FORM OF CONVERTIBLE PROMISSORY NOTE

 

THIS NOTE HAS NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED OR APPLICABLE STATE SECURITIES LAWS. THIS NOTE MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED
OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO THIS NOTE UNDER SAID ACT AND APPLICABLE STATE SECURITIES
LAWS OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.

 

TECOGEN INC.

 

CONVERTIBLE PROMISSORY NOTE

 

	U.S $ ________________	September 24, 200l

 

FOR VALUE RECEIVED, Tecogen Inc.,
a Delaware corporation (the “Company”), hereby promises to pay to the order of _________________
(the “Investor”), on demand on or after September 24, 2004 (the “Payment Date”), subject to the terms
of Section l herein, the principal amount of _________________ Thousand Dollars ($______); plus interest in arrears from and
including the date hereof on the principal balance from time to time outstanding, computed monthly, at a rate per annum equal
to six percent (6%) per annum. This Note may be prepaid in whole or in part, at any time or from time to time, without
premium or penalty. Interest shall be calculated on the basis of actual number of days elapsed over a year of 365 days.
Notwithstanding any other provision of this Note, the Investor (or other holder, as the case may be) does not intend to
charge and the Company shall not be required to pay any interest or other fees or charges in excess of the maximum permitted
by applicable law; any payments in excess of such maximum shall be refunded to the Company or credited to reduce principal
hereunder. Principal and interest hereunder shall be payable in a single payment on demand on or alter the Payment Date.
Capitalized terms used herein but not defined herein shall have the meanings ascribed to diem in the Convertible Note
Purchase Agreement (as defined below).

 

Payments of principal and interest will
be made by wire transfer in immediately available United States funds sent to the Investor (or other holder, as the case may be)
at the address furnished to the Company for that purpose.

 

This Note is one of a series of Convertible
Promissory Notes of like tenor issued by the Company pursuant to and entitled to the benefits of a certain Convertible Note Purchase
Agreement dated as of September 24, 2001 among the Company, the Investor and the other individuals or entities listed on Schedule
l thereto (as the same may be amended from time to time, hereinafter referred to as the “Convertible Note Purchase Agreement”),
and each Investor (or other holder, as the ease may be), by his, her or its acceptance of this Note, agrees to be bound by the
provisions of the Convertible Note Purchase Agreement, including the amendment and waiver provisions set forth in Section 8 therein.
This Note will be registered on the books of the Company or its agent as to principal and interest. Any transfer of this Note will
be effected only by surrender of this Note to the Company and reissuance of a new note to the transferee in accordance with the
terms herein.

 

This Note may be converted into shares of
the Common Stock in accordance with the provisions of the Convertible Note Purchase Agreement.

 

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The Investor (or other holder, as the case
may be) may, prior to maturity of this Note, surrender this Note at the principal office of the Company for transfer or exchange.
Within a reasonable time alter notice to the Company from such Investor (or other holder, as the case may be) of his, her or its
intention to make such exchange and without expense to such Investor (or other holder, as the case may be), except for any transfer
or similar tax which may be imposed on the transfer or exchange, the Company shall issue in exchange therefor another note or notes
(each, a “Transferee Note”) for the same aggregate principal amount as the unpaid principal amount of the Note so surrendered,
having the same maturity and rate of interest, containing the same provisions and subject to the same terms and conditions as the
Note so surrendered. Each Transferee Note shall be made payable to such person or persons, or transferees, as the holder of such
surrendered Note may designate, and such transfer or exchange shall be made in such a manner that no gain or loss of principal
or interest shall result therefrom. The Company may elect not to permit a transfer of the Note if it has not obtained satisfactory
assurance from the Investor (or other holder, as the case may be) that such transfer: (a) is exempt from the registration requirements
of, or covered by an effective registration statement under, the Securities Act of l933, as amended, and the rules and regulations
thereunder, and (b) is in compliance with all applicable state securities laws, including without limitation receipt of an opinion
of counsel for the Investor (or other holder, as the case may be), which opinion shall be satisfactory to the Company.

 

Upon receipt of evidence reasonably satisfactory
to the Company of the loss, theft, destruction or mutilation of this Note, the Company will issue a new Note, of like tenor and
amount and dated the date to which interest has been paid, in lieu of such lost, stolen, destroyed or mutilated Note, and in such
event the Investor (or other holder, as the case may be) agrees to indemnity and hold harmless the Company in respect of any such
lost, stolen, destroyed or mutilated Note.

 

The Company agrees subject only to limitations
imposed by applicable law, to pay the Investor’s or other holder’s, as the case may be, reasonable costs in collecting
and enforcing this Note, including reasonable attorney's fees.

 

No waiver of any obligation of the Company
under this Note shall be effective unless it is in a writing signed by the Investor (or other holder, as the case may be). A right
or remedy under this Note on any occasion shall not be a bar to exercise of the same right or remedy on any subsequent occasion
or of any other right or remedy at any time.

 

All notices, requests, demands and other
communications provided for hereunder shall be in writing (including facsimile and email communications) and mailed, sent by facsimile,
entailed, sent by a recognized overnight air express service or delivered:

 

If to an Investor: at the address set forth
in Schedule l to the Convertible Note Purchase Agreement listing the Investors or at such other address as to which such investor
may inform the other parties in writing.

 

If to the Company; at the address set forth
below, or at such other address as shall be designated by the Company in a written notice to the other parties complying as to
delivery with the terms of this Section 15;

 

Tecogen Inc.

Attention: Chief Executive Officer

85 First Avenue

Waltham, MA 02451

Fax: 781-622—1027 Email: apacheco@thermo.com

 

with a copy to:

 

William O. Flannery, Esq.

722 Grove Street

Framingham, MA 01701

Fax: 508-877-8211 Email: woflan@ix.netcom.com

 

All such notices, requests, demands and
other communications shall (a) when sent by email or facsimile, be effective when sent, (b) when sent by mail (certified mail,
return receipt requested, postage prepaid), overnight air express service or delivery, be effective when received.

 

This Note applies to, inures to the benefit
of`, and binds the successors and assigns of the parties hereto.

 

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This Note shall be governed by and construed
in accordance with the internal laws, and not the laws of conflicts, of the Commonwealth of Massachusetts.

 

In the event any one or more of the provisions
of this Note shall for any reason be held to be invalid, illegal or unenforceable, in whole or in part or in any respect, or in
the event that any one or more of the provisions of this Note operate or would prospectively operate to invalidate this Note, then
and in any such event, such provision(s) only shall be deemed null and void and shall not affect any other provision of this Note
and the remaining provisions of this Note shall remain operative and in full force and effect and in no way shall be affected,
prejudiced, or disturbed thereby,

 

IN WITNESS WHEREOF, the undersigned has
caused this instrument to be executed by its duly authorized officer as of the date fist above written.

 

	 	TECOGEN INC.	 
	 	 	 	 
	 	By:	 	 
	 	Name:	 	 
	 	Title:	 	 

 

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Appendix A

 

(To Be Executed by the Investor or other
holder

in order to convert the Note)

 

CONVERSION NOTICE

FOR

CONVERTIBLE PROMISSORY NOTE

 

The undersigned, as Holder of the
Convertible Promissory Note dated September 24, 2004 of Tecogen Inc. (the “Company”), in the outstanding
principal amount of $_______ (the “Note”), hereby irrevocably elects to convert $ M_ of the outstanding principal amount
of the Note (including all interest accrued with respect to such outstanding principal amount) into shares of Common Stock,
par value $.01 (the “Common Stock”), of the Company according to the conditions of the Note, as of the date
written below. The undersigned hereby requests that share certificates for the Common Stock to be issued to the undersigned
pursuant to this Conversion Notice be issued in the name of; and delivered to, the undersigned or its designee as indicated
below. If shares are to be issued in the name of a person other than the undersigned, the undersigned will pay all transfer
taxes payable with respect thereto. No fee will be charged to the Holder for any conversion, except for transfer taxes, if
any.

 

	Conversion Information:	NAME OF HOLDER:	 
	 	 	 	 
	 	By:	 	 
	 	Print Name:
	 	Print Title:
	 	 	 	 
	 	Print Address of Holder:
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	Issue Common Stock to:	 
	 	 	 	 
	 	Address:	 	 
	 	 	 	 
	 	Date of Conversion:	 

 

    	4Exhibit 10.8

 

Atlantic-Waltham Investment II, LLC

Commercial Lease

 

In consideration of the covenants herein
contained, ATLANTIC-WALTHAM INVESTMENT II, LLC, a Delaware Limited Liability Company, with a usual place of business c/o Atlantic
Management Corporation, 205 Newbury Street, Framingham, Massachusetts 01701, hereinafter called LESSOR, which expression shall
include successors and assigns where the context so admits, does hereby lease to Tecogen Inc., a Delaware corporation, with a usual
place of business at 45 First Avenue, Waltham, MA 02451, hereinafter called LESSEE, which expression shall include successors,
executors, administrators, and assigns where the context so admits, and LESSEE hereby leases from LESSOR the premises hereinafter
described, from the Lease Commencement Date until the Lease Termination Date (the Lease Term) as hereinafter specified, subject
to the terms and conditions hereinafter set forth:

 

1. SUMMARY OF TERMS

 

Description of the Leased Premises: The
premises located at 45 First Avenue, Waltham, Massachusetts (hereinafter the “Leased Premises”) as shown on Exhibit
A attached hereto and incorporated herein. The Leased Premises contains approximately 43,000 rentable square feet (hereinafter
the “Total Rentable Floor Area of the Leased Premises”).

 

	Lease Term:	Five (5) Years
	Lease Commencement Date:	April 1, 2009
	Rent Commencement Date:	April 1, 2009
	Lease Termination Date:	March 31, 2014
	Use of Lease Premises:	Warehouse, manufacturing, distribution facility, offices, and uses incidental thereto

 

	Annual Base (Fixed) Rent for the Lease Term:
	Years 1-2:	43,000 s.f  X $10.50/s.f = $451,500.00 per year or $37,625.00 per month
	Year 3-5:	43,000 s.f  X $11.50/s.f = $494,500.00 per year or $41,208.33 per month

 

	Security Deposit:	$37,625.00
	Building Total Square Footage:	43,000 Rentable Square Feet
	Brokers:	None

 

LESSOR and LESSEE now covenant and agree
that the following terms and conditions shall given this Lease during the Lease Term hereof and for such further time as LESSEE
shall hold the Leased Premises.

 

2. LEASE TERM

 

The Lease Term shall commence on the Lease
Commencement Date, unless such date is advanced or extended as herein provided, and continue until the Lease Termination Date.
LESSEE shall have access to the Leased Premises commencing on the Lease Commencement Date, for the purposes of preparing the Leased
Premises for LESSEE’s occupancy.

 

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3. RENT

 

Commencing on the Rent Commencement Date,
LESSEE shall pay to LESSOR, without any offset or deduction whatever except as made in accordance with the provisions of this Lease,
the Annual Fixed Rent as specified in Article 1 above in monthly installments at the rate of 1/12 of the Annual Fixed Rent as set
forth in Article 1, payable in advance on the first day of each calendar month, the first monthly payment to be made upon execution
of this Lease, including payment in advance of appropriate fractions of a monthly payment any portion of a month at the commencement
of said Lease Term. All payments are to be made to ATLANTIC-WALTHAM INVESTMENT II, LLC, c/o Atlantic Management Corporation, 205
Newbury Street, Framingham, MA 01701. Within (10) days after the Rent Commencement Date, the parties shall complete and execute
a certificate (the “Data Certificate”) attached hereto as Exhibit “B” “Data Certificate” specifying
the date of the actual Rent Commencement Date and the date of the expiration Date of the term. When so complete executed by the
parties, the Data Certificate shall be incorporated herein by reference, and for the purposes of this Lease, the information recited
therein shall be conclusive as to the terms to which they respectively apply; provided, however, the failure of the parties, for
whatever reason to execute the Data Certificate shall not in any way affect the operation validity of the Lease.

 

4. SECURITY DEPOSIT

 

The Lessee agrees to deposit with Lessor
a security deposit in the amount of $37,625.00 upon execution and delivery of this Lease, and that the Lessor shall hold the same,
throughout the term of this Lease, as security for the performance by the Lessee of all obligations on the part of the Lessee to
be kept and performed, subject to the provisions set forth below. The Lessor shall have the right from time to time, without prejudice
to any other remedy the Lessor may have on account thereof, to apply such deposit, or any part thereof, to the Lessor's damages
arising from any default on the part of the Lessee. Upon such application the amount so applied shall be paid by Lessee to Lessor
upon demand in order that the security deposit may at all times be equal to the amount set forth in Section 1. Provided the Lessee
not then being in default, the Lessor shall return the deposit, or so much thereof as shall not have theretofore been applied in
accordance with the terms of this Section 4, to the Lessee within thirty (30) days after the expiration or earlier termination
of the Lease Term and surrender of possession of Premises by the Lessee to the Lessor at such time. The Lessor shall have no obligation
to pay interest on the deposit and shall have the right to commingle the same with the Lessor's other funds. If the Lessor conveys
the Lessor's interest under this Lease, the deposit, or any part thereof not previously applied, may be turned over by the Lessor
to the Lessor's grantee, and, if so turned over, the Lessee agrees to look solely to such grantee for proper application of the
deposit in accordance with the terms of this Section 4, and the return thereof in accordance herewith. The Lessee agrees that the
Lessee will not assign, encumber or pledge, attempt to assign, encumber or pledge the moneys deposited herein as security, and
that neither the Lessor, nor its successors and assigns, shall be bound by any such assignment, encumbrance or pledge, attempted
assignment, attempted pledge, or attempted encumbrance. The holder of a mortgage of property which includes the Premises shall
not be responsible to the Lessee for the return or application of any such deposit, whether or not it succeeds to the position
of the Lessor hereunder, unless such deposit shall have been received in hand by such holder.

 

5. USE OF PREMISES

 

LESSEE shall use the Leased Premises only
for the purposes specified in Article 1 and for no other purpose.

 

6. PREPARATION OF PREMISES FOR OCCUPANCY

 

LESSOR shall deliver the Premises to the
LESSEE in its “as is” condition, provided however, that prior to delivery of the Premises, the Lessor shall replace
the current roof and repair all damage to the ceiling tiles of the Leased Premises caused by existing leaks in the roof. Upon Landlord’s
completion of the replacement and repair, Landlord shall notify Tenant that Landlord’s work is complete, and together with
such notice shall provide Tenant with an invoice for $80,000.00, representing Tenant’s share of the cost of such work, and
Tenant shall pay such invoice within thirty (30) days after its receipt thereof.

 

7. TAXES

 

With reference to the Taxes, it is agreed
that:

 

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LESSOR shall be responsible for the payment,
before the same becomes delinquent, of all general and special taxes, including assessments for local improvements, and other governmental
charges which may be lawfully charged, assessed or imposed (herein collectively called the “Taxes”) upon the Building
and the Lot. However, if authorities having jurisdiction assess real estate taxes, assessments or other charges which LESSOR considers
excessive, LESSOR may defer compliance therewith to the same extent permitted by the laws of the jurisdiction in which the same
are located, so long as the validity or amount thereof is contested by LESSOR in good faith, and so long as LESSEE's occupancy
of the Premises is not disturbed. The initial estimated payment for Taxes for fiscal year 2008, shall be $56,526.24 per year ($4,710.52
per month), or $1.31 per square foot

 

a)             The LESSEE shall pay to the LESSOR Taxes for the Lease
Year within thirty (30) days upon LESSEE’s receipt of written notice from LESSOR containing a receipt from the applicable
municipal authority evidencing that such Taxes have been paid in full.

 

b)             An equitable adjustment shall be made in such figures
with respect to the first and last years of the term hereof in the event that they shall not coincide with the tax year; and an
equitable adjustment shall be made in the event of any change in the method or system of taxation from that which is now applicable,
including the dates and period for which such taxes are levied, or otherwise. Where the applicable tax bill is not available prior
to the end of the term hereof, then the aforesaid adjustment shall be made, tentatively, on the basis of the last year's taxes,
and the amount due shall be treated as an addition to the rent for the last month of the term of the Lease; and final adjustment
shall be made between LESSOR and LESSEE promptly after LESSOR shall have received the tax bill for such period.

 

c)             If some method or type of taxation or assessment shall
replace in whole or in part, the current method of assessment of real estate taxes, or the type thereof, LESSEE agrees that LESSEE
shall pay LESSEE's equitable share of the same computed in a fashion consistent with the method of computation herein provided,
to the end that LESSEE's cost on account thereof shall be, to the maximum extent practicable, the same as LESSEE would bear under
the foregoing paragraphs.

 

If a tax (other than a net income tax) is
assessed on account of the rents or other charges payable by LESSEE to LESSOR under this lease, LESSEE agrees to pay the same within
ten (10) days after billing therefore, unless applicable law prohibits the payment of such tax by the LESSEE. LESSEE's obligation
to make payment of the same shall be applicable irrespective of the party to which the tax is assessed.

 

8. OPERATING COSTS

 

Lessee shall pay to the Lessor as Additional
Rent hereunder: all of the operating costs incurred during the calendar year with respect to the Building of which the Premises
are a part (collectively “Lessee's Share”).

 

The term “Operating Costs” shall
mean all reasonable costs incurred and expenditures made by the Lessor in the operation and management of the buildings and the
associated land comprising the Property, exclusive of capital expenditures, leasing commissions, special services to other lessees,
financing expenses, costs and expenses incurred by Lessor arising from the performance of Lessor's obligations hereunder (but not
excluding costs incurred by Lessor for which Lessee is responsible if not otherwise separately billed), and real estate taxes billed
in accordance with Paragraph 7 herein, as determined in accordance with generally accepted accounting principles. Operating Costs
include, without limitation all reasonable, costs of cleaning, maintenance and repairs to the Property, maintenance of the grounds,
snow removal, management fee equal to up to three (3%) percent of Gross Rent, wages, salaries, benefits, payroll taxes and unemployment
compensation insurance for employees of Lessor employed on the Property or of any contractor of Lessor engaged in the cleaning,
operation, maintenance or security of the Property, insurance relative to the Property, payments other than taxes to the municipality
in which the Property is located, including, but not limited to, water and sewer charges, supplies, insurance and all other expenses
customarily incurred in connection with the operation of buildings of comparable type and use. Lessee shall have the right on an
annual basis to review the Operating Costs, and upon written notice to Lessor, to assume responsibility for any or all of the items
included in the Operating Costs schedule. A list of the current operating costs is attached as Exhibit E.

 

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Lessee’s Share shall be due and payable
within twenty (20) days following receipt by Lessee of the Operating Escalation Statement for such year. Upon request of Lessee,
Lessor shall provide Lessee with reasonable documents supporting Lessee's Share of Operating Costs. Lessee shall pay to Lessor,
as estimated payments of the Operating Costs, one-twelfth (1/12) of the sum, if any, shown to be due in the Operating Cost budget
for the previous calendar year. If this Lease shall commence or expire in the middle of a calendar year Lessee shall be liable
for only that portion of the Operating Cost excess in respect to such calendar year as is represented by a fraction the numerator
of which is the number of days of the Term which falls within the calendar year and the denominator of which is three hundred sixty-five
(365). The initial estimated Operating Costs for 2009 shall be $56,486.00 as shown on Exhibit E, or $4,707.17 per month, and $1.31
per square foot).

 

The LESSEE shall pay to the LESSOR pro rata
monthly installments on account of projected Operating Costs for the Lease Year, calculated by the LESSOR on the basis of the most
recent Operating Costs data or budget available, with an adjustment made to the account for actual Operating Costs for such Lease
Year. If the total of such monthly installments in any Lease Year is greater than the actual Operating Costs for such Lease Year,
the LESSEE shall be entitled to a credit against the LESSEE's base rental obligations hereunder in the amount of such difference.
If the total of such monthly installments is less than the actual Operating Costs for such Lease Year, the LESSEE shall pay to
the LESSOR the amount of such difference promptly upon billing therefor.

 

For the purposes of this Article “Lease
Year' shall mean any fiscal year from January 1 to December 31, except that the first Lease Year during the term of this Lease
shall commence on the Commencement Date and end on the next following December 31 and the last Lease Year during the term of this
Lease shall end on the date this Lease terminates (each of such first and last Lease Years are referred to in the immediately preceding
paragraph (b) as a “Partial Lease Year”);

 

Operating Costs shall be computed on an
“as paid” basis and shall be determined in accordance with generally accepted accounting principles consistently applied.
They may be incurred directly or by way of reimbursement, and shall include taxes applicable thereto. The following shall be excluded
from Operating Costs:

 

(1)         Salaries
of officers and executives of the LESSOR not connected with the Operation of the Property;

(2)         Depreciation;

(3)         Expenses
relating to LESSEES' alterations;

(4)         Interest
on indebtedness;

(5)         Expenses
for which the LESSOR, by the terms of this Lease or any other lease, makes a separate charge; and

(6)         Leasing
fees or commissions.

 

All Operating Costs shall be reduced by
the amount (net of collection costs) of any insurance reimbursement, discount or allowance received by the LESSOR in connection
with such costs.

 

9. LATE PAYMENT

 

LESSEE shall pay interest (which shall be
considered additional rent) at an annual rate which shall be the lesser of twelve (12) percent or the maximum rate allowed by law,
from the date due, for any installment of Annual Fixed rent, additional rent, or other payment which is not received by LESSOR
within ten days of said due date.

 

10. UTILITIES

 

The Lessee shall pay, during the term as
they become due, all bills for electricity and other utilities (including those that are used for furnishing heat or other purposes)
that are furnished to the Premises and are presently separately metered, and all bills for fuel furnished by a separate tank servicing
the Premises exclusively. The Lessor agrees to provide all other utility service (except to the extent that the same are furnished
through separately metered utilities or separate fuel tanks as set forth above) to the Premises, and to furnish reasonable hot
and cold water to the Premises' lavatories, twenty four hours a day, seven days a week, and to light any common passageways and
common stairways during business hours, all subject to interruption due to the making of repairs, alterations, or improvements,
and due to circumstances beyond Lessor's control such as accidents, labor difficulties, trouble in obtaining fuel, electricity,
service, or supplies from the sources from which they are usually obtained for said Building, or to any other cause beyond the
Lessor's reasonable control.

 

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11. COMPLIANCE WITH LAWS

 

LESSEE acknowledges that no trade, occupation,
or activity shall be conducted in the Leased Premises or use made thereof which will be unlawful, improper, noisy or offensive,
or contrary to any statute, regulation, or ordinance in force in the city or town in which the Leased Premises are situated. LESSEE
shall keep all employees working in the Leased Premises covered with Worker's Compensation Insurance in accordance with law. LESSEE
shall be responsible for causing the premises and any work conducted therein to be in full compliance with the Occupational Safety
and Health Act of 1970 and any amendments thereof.

 

12. FIRE INSURANCE

 

LESSEE shall not permit any use of the Leased
Premises which will adversely affect, increase the premium of, or make voidable, any insurance on the Property or on any building
or portion of the Property or the contents thereof, or which shall be contrary to any law or regulation from time to time established
by the Insurance Services Office (or successor), local Fire Department, or any similar body. LESSEE shall on demand reimburse LESSOR,
and all other lessees, all extra insurance premiums caused by LESSEE's use of the premises. LESSEE shall not vacate the Leased
Premises or permit same to be unoccupied other than during LESSEE's customary non-business hours.

 

13. MAINTENANCE OF PREMISES/STRUCTURAL OBLIGATIONS/CLEANING

 

13.1 LESSEE’s Obligations.

 

From and after the date that possession
of the Premises is delivered to the LESSEE and until the end of the Lease Term, the LESSEE shall keep the Premises and every part
thereof, in good order, condition and repair, reasonable wear and tear and damage by unavoidable casualty only excepted; and the
LESSEE shall surrender the Premises at the end of the Lease Term in such condition.

 

Whenever the LESSEE shall make repairs,
alterations, decorations, additions, removals, or improvements (including the installation of any equipment other than normal light
business office equipment) in or to the Premises:

 

a)             Any mechanic's or materialmen's lien filed against
the Premises or the Building for work claimed to have been done for, or materials claimed to have been furnished to the LESSEE,
shall be immediately discharged by the LESSEE, at the LESSEE's expense, by filing the bond required by law or otherwise. If the
LESSEE fails so to discharge any lien, the LESSOR may do so at the LESSEE's expense and the LESSEE shall reimburse the LESSOR for
all expenses and costs incurred by the LESSOR in so doing immediately after rendition of a bill therefor by the LESSOR to the LESSEE;

 

b)             All installations or work done by or for the LESSEE
shall be at its own expense and shall at all times comply with (i) laws, rules, orders and regulations of governmental authorities
having jurisdiction thereof; (ii) orders, rules and regulations of any Board of Fire Underwriters, or any other body hereafter
constituted exercising similar functions, and governing insurance rating bureaus; (iii) plans and specifications (which shall be
prepared by and at the expense of the LESSEE) theretofore submitted to and approved in writing by the LESSOR;

 

c)             The LESSEE shall procure all necessary permits before
undertaking any work in the Premises and shall do all such work in a good and workmanlike manner, employing new materials of first
class quality and shall defend, save harmless, exonerate and indemnify the LESSOR from all injury, loss or damage to any person
or property occasioned by such work. The LESSEE shall cause contractors employed by the LESSEE to carry and maintain in force during
the continuance of any work being performed for the LESSEE Worker's Compensation Insurance in accordance with statutory requirements
and Comprehensive Public Liability Insurance and Automobile Liability Insurance covering such contractors on or about the Premises
in amounts reasonably acceptable to the LESSOR and to submit certificates evidencing such coverage to the LESSOR prior to the commencement
of such work; and

 

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d)             The LESSEE shall not, at any time prior to or during
the Term of the Lease, directly or indirectly employ, or permit the employment of, any contractor, mechanic or laborer in the Premises,
whether in connection with any repair work or the making of any alteration, improvements or additions or otherwise, if such employment
will interfere or cause any conflict with other contractors, mechanics, or laborers engaged in the construction, maintenance or
operation of the Building by the LESSOR, LESSEE or others. In the event of any such interference or conflict, the LESSEE, upon
demand of the LESSOR shall cause all contractors, mechanics or laborers causing such interference or conflict to leave the Building
immediately.

 

13.2 LESSOR Services

 

The Lessor agrees to maintain, repair and
replace (as necessary) the structure and foundation of the Building, the roof (except for repairs thereto necessitated by Lessee's
installation, repair, maintenance or replacement of equipment located on the roof), the parking and access ways, and other common
areas, in the same condition as they are on the Commencement Date or as they may be put in during the term of this Lease, reasonable
wear and tear, damage by fire and other casualty only excepted, unless such maintenance is required because of the conduct of Lessee
or those for whose conduct the Lessee is legally responsible (including, but not limited to loading dock, dock bumpers, dock enclosures,
if applicable). Lessor shall maintain provide to the Premises all of the services whose costs are included in the definition of
Operating Expenses under Paragraph 8 other than those services specifically assumed by Lessee.

 

The LESSOR shall furnish water at City temperature
for fire protection, ordinary cleaning, toilet, lavatory and drinking purposes. If the LESSEE uses or consumes water for any other
purpose, it shall reimburse the LESSOR therefor, and for any related sewer charge, as reasonably estimated by the LESSOR or, at
its election, metered. In the latter event, the LESSEE shall pay the cost of the meter and its installation and maintenance. Such
reimbursement shall be made as and when bills are rendered. All water piping and equipment shall be installed and maintained by
the LESSOR at the LESSEE's expense. LESSEE shall also reimburse LESSOR for any utilities costs incurred with respect to the Premises.
LESSEE may, at its option, have such utilities separately metered.

 

14. ALTERATIONS

 

LESSEE shall not make structural alterations
or additions of any kind to the Leased Premises, but may make nonstructural alterations provided LESSOR consent thereto in advance
in writing, which consent shall not be unreasonably withheld provided said alterations are consistent in appearance and quality
with the rest of the Building and Property. However, LESSOR shall not be obligated to approve any such alterations which would
subject LESSOR to additional expense to readapt or prepare the Leased Premises for re-leasing upon the termination of this Lease
or which would increase the Real Estate Tax Expenses of the Property. All such allowed alterations shall be at LESSEE's sole risk
and expense, shall conform with LESSOR's construction specifications, shall be performed in good and workmanlike manner, and shall
comply with all applicable codes and regulations. If LESSOR performs any services for LESSEE in connection with such alterations
or otherwise, any just invoice will be considered additional rent and will be promptly paid. LESSEE shall not permit any mechanics'
liens, or similar liens, to remain upon the Leased Premises in connection with work of any character performed or claimed to have
been performed at the direction of LESSEE and shall cause any such lien to be released or removed without cost to LESSOR within
ten (10) days of written request by LESSOR. Any alterations or improvements shall become part of the real estate and the property
of LESSOR. LESSEE shall remove any alteration or addition made by it and restore the Leased Premises and other affected area(s),
if any, to the same condition as they were in on the Lease Commencement Date upon the expiration or termination of this Lease if
LESSOR so directs. Any alterations completed by LESSOR shall be “building standard” unless noted otherwise. LESSOR
shall have the right at any time to change the arrangement and layout of parking areas, stairs, walkways, common areas and other
areas of the Property not contained within the Leased Premises, to install, repair, replace, remove, use, maintain and relocate
for service to the Leased Premises and to other parts of the Property, pipes, ducts, conduits, wires and fixtures wherever located
inside or outside of the Building and the Property, to change the boundaries of the lot upon which the Building is located, to
construct additions to existing buildings on the Property, and to construct additional buildings and improvements on the Property.

 

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15. ASSIGNMENT OR SUBLEASING

 

LESSEE shall not assign, mortgage, pledge,
hypothecate or otherwise transfer this Lease or sublet (which term, without limitation, shall include granting of concessions,
licenses, and the like) or allow any other firm or individual to occupy the whole or any part of the Leased Premises without the
prior written consent of LESSOR, or suffer or permit this Lease or the leasehold estate hereby created or any other rights arising
under this Lease to be assigned, transferred, or encumbered, in whole or in part, whether voluntarily, involuntarily, or by operation
of law. LESSOR’s consent shall not be unreasonably withheld or delayed, subject to the conditions contained in this Paragraph
15. In the event of any intent to assign this Lease or sublet any portion or all of the Leased Premises, LESSEE shall notify LESSOR
in writing of LESSEE's intent and the proposed effective date of such subletting or assignment, and shall request in such notification
that LESSOR consent thereto. LESSEE will reimburse LESSOR, as additional rent, for reasonable legal and other expenses incurred
by LESSOR in connection with any request by LESSEE for consent to assignment or subletting. In the event that the fixed rental
to be paid by any subLESSEE, assignee or transferee of LESSEE shall exceed Annual Fixed Rent as set forth in Article 3 herein payable
by LESSEE to LESSOR, or in the event that any subLESSEE, assignee or transferee shall pay to LESSEE a sum of money in consideration
for such sublease, assignment or transfer, then LESSEE shall pay one-half (1/2) to LESSOR, as additional rent, a sum equal to the
amount by which the fixed rent payable by such subLESSEE, assignee or transferee exceeds the Annual Fixed Rent payable under Article
3 herein or an amount equal to such sum of money. Provided, however, that the provisions of the previous sentence shall not apply
to any assignments or subletting to LESSEE’s subtenants listed below and their affiliated companies (American DG Energy Inc.,
Alexandros Partners LLC, Pharos, LLC, Levitronix LLC, Levitronix Medical LLC, Levitronix Technologies LLC, Levitronix IP LLC, Tecogen
Inc., HR Knowledge). No assignment or subletting and no consent of LESSOR thereto shall affect the continuing primary liability
of LESSEE (which, following assignment shall be joint and several with the assignee) for the payment of all rent and for the full
performance of the covenants and conditions of this Lease. No consent to any of the foregoing in a specific instance shall operate
as a waiver in any subsequent instance, and no assignment shall be binding upon LESSOR or any of the LESSOR's mortgagees, unless
LESSEE shall deliver to LESSOR an instrument in recordable form which contains a covenant of assumption by the assignee running
to LESSOR and all persons claiming by, through or under LESSOR, but the failure or refusal of the assignee to execute such instrument
of assumption shall not release or discharge assignee from its liability as a LESSEE for the payment of all rent and for the full
performance of the covenants and conditions of this Lease, nor shall execution of such instrument of assumption affect the continuing
primary liability of LESSEE for the payment of all rent and for the full performance of the covenants and conditions of this Lease.
LESSOR has pre-approved the following subtenants and their affiliated companies: American DG Energy Inc., Alexandros Partners LLC,
Pharos, LLC, Levitronix LLC, Levitronix Medical LLC, Levitronix Technologies LLC, Levitronix IP LLC, Tecogen Inc., HR Knowledge.

 

16. SUBORDINATION

 

LESSEE agrees at the request of LESSOR to
subordinate this Lease to any first mortgage or other security interest hereafter created covering the Leased Premises or any portion
of the Leased Premises and to any renewal, modification, replacement or extension or any existing first mortgage, or any mortgage
or security interest hereinafter created and to any and all advances made or to be made thereunder, provided that the mortgagee
or holder of such security interest agrees, for itself and its successors and assigns in writing with the LESSEE that so long as
LESSEE shall not be in default under this Lease, the mortgagee or other holder of such security interest and its successors and
assigns will not disturb the peaceful quiet enjoyment of the Leased Premises by the LESSEE. LESSEE also agrees that if this Lease
is so subordinated, no entry under any mortgage or sale for the purpose of foreclosing the same shall be regarded as an eviction
of LESSEE, constructive or otherwise, or give LESSEE any right to terminate this Lease, whether it attorns or becomes LESSEE of
the mortgagee or new owner, and such mortgage, or security interest to which this Lease shall become subordinated may contain such
other terms, provisions and conditions as are usual and customary. LESSEE agrees that it will, within ten (10) days of receipt
of written request of the LESSOR, execute and deliver any and all instruments necessary or desirable to give effect to or notice
of such subordination in such forms as may be required by such mortgagee or other holder of such security interest.

 

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17. ESTOPPEL CERTIFICATES

 

Upon ten (10) days prior written request
by LESSOR, LESSEE agrees to execute and deliver an estoppel certificate certifying that this Lease is unmodified and in full force
and effect (or, if there have been any modifications that this Lease is in full force and effect as modified and stating the modifications)
and the dates to which the Annual Fixed Rent, additional rent and other charges have been paid through and any other information
reasonably requested. Any such statement delivered pursuant to this Article may be relied upon by any prospective purchaser, mortgagee
or lending source.

 

18. LESSOR'S ACCESS

 

LESSOR or agents of LESSOR may at reasonable
times enter to view the Leased Premises and may remove at LESSEE's expense any signs, alterations or additions not approved and
constructed or installed as herein provided, may make such repairs and alterations as LESSOR may deem necessary to avert an emergency,
may make any repairs which LESSEE is required but has failed to do, and may show the leased premises to others.

 

19. ACCESS AND PARKING

 

LESSEE shall have the right, without additional
charge, to use all of the parking spaces located within the parking area provided for the Leased Premises. LESSEE may not sublease
any parking space so allocated. Said parking area plus any stairs, walkways or other common areas shall in all cases be considered
extensions of the Leased Premises to the extent that they are utilized by LESSEE, or LESSEE's employees, visitors or business invitees.
LESSEE will not obstruct in any manner any portion of the Building or the Property, or the walkways or approaches to said Building
or Property, and will conform to all reasonable rules now or hereafter made by LESSOR for parking, and for the care, use, or alteration
of the Property, its facilities and approaches. LESSOR shall have the right to impose reasonable controls on the operation of the
parking area.

 

LESSEE further warrants that LESSEE will
not permit any employee, visitor or invitee to violate this or any other covenant or obligation of LESSEE. No vehicle shall be
stored or left in any parking area for more than fourteen consecutive nights without LESSOR's written approval. Unregistered or
disabled vehicles, or storage trailers of any type, may not be parked overnight at any time. LESSEE agrees to assume all expense
and risk for towing of any mis-parked vehicle belonging to LESSEE or LESSEE's agents, employees, business invites, or callers,
at any time.

 

20. LESSEE'S LIABILITY INSURANCE

 

LESSEE will secure and carry at its own
expense a comprehensive general liability policy insuring LESSEE AND LESSOR against any claims based on bodily injury (including
death) or property damage arising out of the condition of the Leased Premises or their use by LESSEE, such policy to insure LESSEE
and LESSOR against any claim up to Two Million Dollars ($2,000,000) per occurrence for injury or death to one person, and One Million
Dollars ($1,000,000) for damage to property. Such limits shall be subject to increase from time to time during the Lease Term.
The amount of such insurance shall not limit LESSEE's liability nor relieve LESSEE of any obligation hereunder.

 

Upon commencement of the Lease Term LESSEE
will promptly file with LESSOR certificates reasonably satisfactory to LESSOR showing that such insurance is in force, accompanied
by evidence of the payment of the premium for the policy, and thereafter will file renewal certificates at least thirty (30) days
prior to the expiration of any such policies. All such insurance certificates shall provide that such policies shall not be canceled
nor materially changed without at least twenty (20) days prior written notice to each assured named therein. LESSEE may, at LESSEE's
cost, maintain such other liability insurance as LESSEE may deem necessary to protect it.

 

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LESSEE shall assume exclusive control of
the Leased Premises, and all tort liabilities incident to the control or ownership thereof, and agrees to indemnify and hold the
LESSOR free and harmless from any and all liability, penalties, losses, damages, costs and expenses, causes of action, claims or
judgments or encumbrances created or suffered by the LESSEE, and from any and all liability, penalties, losses, damages, costs
and expenses, causes of action, claims, or judgments arising from injury to persons or property of any nature on the Leased Premises
or the Property, occasioned by any acts or omissions of the LESSEE or of its employees, agents, invitees, visitors, callers, servants,
sub lessees, or independent contractors, and arising out of the use or occupation of said Leased Premises or by reason of the bursting
or leakage of pipes; from any neglect or misuse on the Leased Premises or by any reason of nuisance made or suffered on the Leased
Premises; and also against all legal costs and charges, including counsel fees, reasonably incurred in and about such matters and
the defense of any action arising out of the same, or in discharging the Leased Premises or any part thereof from any and all liens
that may be placed thereon from charges incurred by LESSEE. If LESSOR intervenes in or becomes a party to any such action or actions
growing out of this Lease to protect its rights, then the LESSEE shall pay LESSOR's reasonable attorney's fees in such action or
actions.

 

21. WAIVER OF SUBROGATION

 

Any casualty and liability insurance carried
by LESSEE pursuant to Paragraph 20, shall include a clause or endorsement denying to the insurer rights of subrogation against
the other party to the extent rights have been waived by the insured prior to the occurrence of injury or loss. Each party, notwithstanding
any provisions of this Lease to the contrary, hereby waives any rights of recovery against the other for injury or loss due to
hazards covered by such insurance containing such antisubrogation clause or endorsement to the extent of the indemnification received
thereunder.

 

22. FIRE, CASUALTY, EMINENT DOMAIN

 

Should a substantial portion of the Leased
Premises, or of the Property, be substantially damaged by fire or other casualty, or by action of public or other authority in
consequence thereof, or be taken by eminent domain, or should LESSOR receive compensable damage by reason of anything lawfully
done in pursuance of public or other authority, this Lease shall terminate at either party's election, which may be made notwithstanding
LESSOR's entire interest may have been divested, by written notice given to the other within sixty (60) days after the occurrence
of the event giving rise to the election to terminate, which notice shall specify the effective date of termination.

 

The effective date of any termination by
either party under this Article shall be not less than fifteen (15) nor more than thirty (30) days after the date of such notice
of the termination. For the purposes of this Article, damage or taking shall be considered substantial if the time needed for LESSOR
to perform repairs and/or construction necessary to put the Leased Premises or such remainder in proper condition for use and occupation
is estimated by LESSOR to exceed six (6) months, or if more than thirty (30) percent of the non-wetlands land area of the Property,
or if more than thirty (30) percent of the Leased Premises are so taken. In case of any such damage or taking, LESSOR shall notify
LESSEE within thirty (30) days after the occurrence thereof of Lessor's estimate of the time needed to perform the repairs and/or
construction necessary to put the Leased Premises or such remainder in proper condition for use and occupancy, or of the percentage
of the non-wetlands land area, or of the Building, or of the Leased Premises taken.

 

If in any such case the Leased Premises
are rendered unfit for use and occupation and the Lease is not so terminated, LESSOR shall use due diligence to put the Leased
Premises, or in case of taking what may remain thereof (excluding any items installed or paid for by LESSEE, which LESSEE may be
required to remove), into proper condition for use and occupation and a just proportion of the Annual Fixed Rent and any additional
rent according to the nature and extent of the injury shall be abated until the Leased Premises or such remainder shall have been
put by Lessor in such condition and in case of a taking which permanently reduced the area of the Leased Premises, a just proportion
of the Annual Fixed Rent and additional rent shall be abated for the remainder of the Lease Term.

 

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LESSOR reserves to itself any and all rights
to receive awards made for damages to the Leased Premises and the Property and the leasehold hereby created, or any one or more
of them, accruing by reason of exercise of eminent domain or by reason of anything lawfully done in pursuance of public or other
authority. LESSEE hereby releases and assigns to LESSOR all of LESSEE's to such awards, and covenants to deliver such further assignments
and assurances thereof as LESSOR may from time to time request. It is agreed and understood, however, that LESSOR does not reserve
to itself, and LESSEE does not assign to LESSOR, any damages payable for (1) movable trade fixtures installed by LESSEE or anybody
claiming under LESSEE at its own expense or fixtures or items the removal of which is required or permitted by any agreement given
pursuant to the Lease, or (ii) relocation expenses recoverable by LESSEE from such authority in a separate action.

 

23. INTERRUPTIONS

 

LESSOR shall not be liable to LESSEE for
any compensation or reduction of rent by reason of inconvenience or annoyance or for loss of business arising from power and other
utility losses, shortages or malfunctions, the necessity of LESSOR's entering the Leased Premises for any of the purposes in this
Lease authorized, or for repairing the Leased Premises or any other portion of the Property however the necessity may occur. In
case Lessor is prevented or delayed from making repairs, alterations or improvements, or furnishing any services or performing
any other covenant or duty to be performed on LESSOR's part, by reason of any and all causes reasonably beyond LESSOR's control,
LESSOR shall not be liable to LESSEE therefor, nor shall LESSEE be entitled to any abatement or reduction of rent by reason thereof,
nor shall the same give rise to a claim in LESSEE's favor that such failure constitutes actual or constructive, total or partial,
eviction from the Leased Premises. LESSOR reserves the right to stop any service or utility system, when necessary by reason of
accident or emergency, or until necessary repairs have been completed, provided, however, that in each instance of stoppage, LESSOR
shall exercise reasonable diligence to eliminate the cause thereof.

 

24. BROKERAGE

 

LESSEE warrants and represents to LESSOR
that LESSEE has dealt with no broker with respect to this Lease and LESSEE agrees to indemnify LESSOR against any brokerage claims
arising by virtue of this Lease, other than from Brokers named herein. LESSOR warrants and represents to LESSEE that LESSOR has
employed no exclusive broker or agent in connection with the letting of the Leased Premises other than the Brokers named herein,
whom it will be LESSOR’s responsibility to pay by separate agreement, and agrees to indemnify LESSEE against any brokerage
claims arising by virtue of this Lease.

 

25. SIGNS

 

LESSEE shall be permitted to display a sign
subject to obtaining the appropriate approvals from the City of Waltham, provided the LESSEE shall, however, first obtain the written
consent of LESSOR, and any approvals required under applicable by-laws or regulations, before erecting any sign on the Property,
and shall obtain written approval as to size, content, appearance, and locations of all authorized signs. All existing signs utilized
by Lessee and its subtenants are hereby approved.

 

26. DEFAULT, BANKRUPTCY AND ACCELERATION OF RENT.

 

In the event that: (a) LESSEE files a petition
for adjudication as a bankrupt or shall be declared bankrupt or insolvent according to law, or if an involuntary petition under
any of the provisions of the Bankruptcy Act is filed against LESSEE and is not dismissed within sixty (60) days thereafter, or
if any assignment shall be made of LESSEE's property for the benefit of creditors or (b) LESSEE shall default the observance or
performance of any of LESSEE's covenants, agreements, or obligations hereunder, other an substantial monetary payments as provided
below, and such default shall not be corrected with fifteen (15) days after written notice thereof; or (c) LESSEE vacates the Leased
Premises or permits them to be unoccupied for a period exceeding 30 days other than during LESSEE's customary non-business hours,
then LESSOR shall have the right thereafter, while such default continues, and without demand or further notice to re-enter and
take complete possession of the Leased Premises, or declare the term of this Lease ended, and to remove LESSEE's effects without
becoming guilty of any manner of trespass, and without prejudice to any remedies which might be otherwise used for arrears of rent
or other default or breach of covenant. In addition to the foregoing, if LESSEE shall default in the payment of the security deposit,
or Annual Fixed Rent, taxes, additional rent, or any other substantial invoice for goods and/or services or other sum herein specified,
and such default shall continue for ten (10) days after written notice thereof, and, because both parties agree that nonpayment
of said sums when due is a considerable and significant breach of the Lease, and, because the payment of rent in monthly installments
is for the sole benefit and convenience of LESSEE, then the entire balance of rent which otherwise accrue hereunder shall, at the
option of LESSOR, become immediately due and payable, and, in addition, LESSOR shall have all other rights of LESSOR, as set forth
in this Article, for a default by LESSEE.

 

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LESSOR, without being under any obligation
to do so and without thereby waiving any default, may remedy same for the account and at the expense of LESSEE. If LESSOR pays
or incurs any obligations for the payment of money in connection therewith, including but not limited to reasonable attorney's
fees in instituting, prosecuting or defending any action or proceeding, such sums paid or obligations incurred plus interest at
the rate of eighteen (18) percent per annum and costs, shall be paid by LESSOR by LESSEE as additional rent. Any sums received
by LESSOR shall be applied first to any unamortized improvements completed for LESSEE's occupancy, then to offset any outstanding
invoice or other payment due to LESSOR, with the balance applied to outstanding rent. Notwithstanding the foregoing, LESSEE agrees
to pay reasonable attorney's fees incurred by LESSOR in enforcing any or all obligations of LESSEE under this Lease at any time.

 

Any and all rights and remedies which LESSOR
may have under this Lease, at law and equity, shall be cumulative and shall not be deemed inconsistent with each other, and any
two or more of all such rights and remedies may be exercised at the same time insofar as permitted by law.

 

27. LIABILITY LIMITATIONS

 

LIABILITY OF LESSOR. LESSEE acknowledges
and agrees that Owner shall not be liable or responsible in any way to LESSEE or any other person for:

 

(i)          any
Injury arising from or out of any occurrence in, upon, at, or relating to the property including the premises, or any part thereof
or any loss or damage to property (including loss of use thereof) of LESSEE or any other Person located on the property including
the premises or any party thereof from any cause whatsoever, whether or not such injury, loss, or damage results from any fault,
default, negligence, act, or omission of Owner or its agents, servants, employees, or any other Person for whom Owner is in law
responsible;

 

(ii)         any
Injury to LESSEE or any other Person or loss or damage to property resulting from: fire; smoke; explosion; falling plaster, ceiling
tiles, fixtures or signs; broken glass; steam; gas; fumes; vapors; odors; dust; dirt; grease; acid; oil; any hazardous material
or substance; debris; noise; air or noise pollution; theft; breakage; vermin; electricity; computer or electronic equipment or
systems malfunction or stoppage; water; rain; flood; flooding; freezing; tornado; windstorm; snow; sleet; hail; frost; ice; excessive
heat or cold; sewage; sewer backup; toilet overflow; or leaks or discharges from any part of the property (including the Premises),
or from any pipes, sprinklers, appliances, equipment (including without limitation, heating, ventilating, and air conditioning
equipment); electrical or other wiring; plumbing fixtures; roof(s), windows, skylights, doors, trapdoors, or subsurface of any
floor or ceiling of any part of the Property, or from the street or any other place, or by dampness or climatic conditions, or
from any other cause whatsoever;

 

(iii)        any
Injury, loss, or damage caused by other LESSEEs or any Person on the property, including the premises, or by occupants of adjacent
property thereto, or by the public, or by construction or renovation, or by any private, public, or quasi-public work, or by interruption,
cessation, or failure of any public or other utility service, or caused by Force Majeure;

 

(iv)        any
Injury to LESSEE or any other Person or any loss or damage suffered to the Premises or the contents thereof by reason of Owner
or its representatives entering the Premises to undertake any work therein, or to exercise any of Owner's rights or remedies hereunder,
or to fulfill any of Owner's obligations hereunder, or in the case of emergency; or

 

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(v)         any
Injury, loss, or damage to property caused by perils insured against or required to be insured against by LESSEE pursuant to Section
20. LESSEE shall promptly indemnify and hold Owner harmless from and against any and all claims in connection with any Injury or
any loss or damage to property referred to in this Section.

 

Notwithstanding anything in this Lease to
the contrary, if the LESSOR shall fail to fulfill any covenant, term or condition of this Lease on LESSOR's part to be performed,
or if LESSOR is guilty of negligence, LESSEE shall recover a money judgment against LESSOR, such judgment shall be satisfied only
out of the proceeds of sale received upon execution of such judgment and levy thereof against the right, title and interest of
LESSOR in 45 First Avenue, Waltham, Massachusetts only, and neither LESSOR, nor any of the Managers, Board of Directors,
Shareholders, or former Limited Partners designated herein, as LESSOR comprising any limited liability corporation designated herein
as LESSOR shall be personally liable for any judgment rendered against the LESSOR or any deficiency thereunder. It is agreed that
in no event shall the LESSEE have any right to levy execution against any other property of the LESSOR including, but not limited
to, any other property owned, managed or controlled by the Limited Partnership, other than its interest in 85 First Avenue, Waltham,
Massachusetts, LESSOR shall be released from all liability and obligation hereunder. IN NO EVENT SHALL LESSOR EVER BE PERSONALLY
LIABLE TO THE LESSEE, OR ANYONE CLAIMING, BY UNDER OR THROUGH THE LESSEE, FOR CONSEQUENTIAL OR LIQUIDATED DAMAGES, SUCH DAMAGES
OR CLAIMS, THEREFORE, BEING HEREBY EXPRESSLY WAIVED BY LESSEE.

 

LIABILITY OF LESSEE. If the LESSEE
fails to fulfill to any covenant, term or condition of this Lease on LESSEE's part to be performed, or if LESSEE is guilty of negligence
with regard to any party claiming by, under or through the LESSOR and, a s a consequence of such default and/or negligence, LESSOR
shall recover a money judgment against LESSEE, such judgment shall be satisfied only out of the proceeds of sale received upon
execution of such judgment and levy thereof against the right, title and interest of the LESSEE Corporation, and non e of the LESSEE
Corporation's officers, directors, shareholders, shall be personally liable for any judgment rendered against the LESSEE or any
deficiency thereunder. It is agreed that in no event shall the LESSOR have any right to levy execution against any other property
of the LESSEE including, but not limited to, any other property or business interest owned, managed or controlled by the LESSEE
Corporation, other than its interest in the business located at the Premises. IN NO EVENT SHALL LESSEE EVER BE PERSONALLY LIABLE
TO THE LESSOR, OR ANYONE CLAIMING BY, UNDER OR THROUGH THE LESSOR, FOR CONSEQUENTIAL DAMAGES, SUCH DAMAGES OR CLAIMS, THEREFORE,
BEING HEREBY EXPRESSLY WAIVED BY LESSOR.

 

28. NO ACCORD AND SATISFACTION

 

No acceptance by LESSOR of a lesser sum
than the Annual Fixed Rent and additional rent then due shall be deemed to be other than on account of the earliest installment
of such rent due, nor shall any endorsement or statement on any check or any letter accompanying any check or payment as rent be
deemed an accord and satisfaction, and LESSOR may accept such check or payment without prejudice to LESSOR's right to recover the
balance of such installment or pursue any other remedy provided in this Lease.

 

29. NOTICES

 

Any notice from LESSOR to LESSEE relating
to the Leased Premises or to the occupancy thereof, shall be deemed duly served, if left at the Leased Premises addressed to LESSEE,
or if sent to the Leased Premises by certified mail, return receipt requested, postage prepaid, addressed to LESSEE. Any notice
from LESSEE to LESSOR relating to the Leased Premises, the occupancy thereof, or this Lease shall be deemed duly served if delivered
to LESSOR by certified mail, return receipt requested, postage prepaid, addressed to LESSOR as follows:

 

ATLANTIC-WALTHAM INVESTMENT II, LLC

c/o Atlantic Management Corporation

205 Newbury Street

Framingham, MA 01701

 

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With a copy to:

Robert Orsi, Esq.

Orsi Arone Rothenberg

160 Gould Street

Needham, MA 02494-2300

 

If to LESSEE:

Tecogen Inc.

45 First Avenue

Waltham, MA 02451

 

With a copy to:

William O. Flannery, Esq.

945 Lenox Road

Richmond, Massachusetts 01254

 

or at such other address as LESSOR may from time to time in
writing designate. Time is of the essence in the delivery any notice.

 

30. OCCUPANCY/HOLDOVER

 

In the event that LESSEE takes possession
of said premises prior to the Lease Commencement Date, LESSEE will perform and observe all of LESSEE's covenants from the date
upon which LESSEE takes possession except the obligation for the payment of extra rent for any period of less than one month. LESSEE
shall not remove LESSEE's goods or property from the Leased Premises other than in the ordinary and usual course of business, without
having first paid and satisfied LESSOR for all rent which may become due during the entire term of this Lease. In the event that
LESSEE continues to occupy or control all or any part of the Leased Premises after the agreed termination date of this Lease without
the written permission of LESSOR, then all other terms of this Lease shall continue to apply except that LESSEE shall be liable
to LESSOR for any and all loss, damages or expenses incurred by LESSOR, and rent shall be due in full monthly installments at a
rate of two hundred (200%) percent of that which would otherwise be due under this Lease, it being understood between the parties
that such extended occupancy as a LESSEE at sufferance is solely for the benefit and convenience of LESSEE and such has greater
rental value. LESSEE's control or occupancy of all or any part of the Leased Premises beyond noon on the last day of any monthly
rental period shall constitute LESSEE's occupancy for an entire additional month, and increased rent as provided in this Article
shall be due and payable immediately in advance.

 

31. FIRE PREVENTION

 

LESSEE agrees to use every reasonable precaution
against fire and agrees to provide and maintain approved, labeled fire extinguishers and emergency lighting equipment within the
Leased Premises as required or recommended by the Insurance Services Office (or successor organization), OSHA, and/or local authorities.

 

32. OUTSIDE AREA

 

No goods, equipment, or things of type or
description shall be held or stored outside the Leased Premises at any time without express written approval from LESSOR. Any goods,
equipment or things left outside the Leased Premises without LESSOR's prior written consent shall be deemed abandoned and may be
removed without notice by LESSOR. LESSEE agrees to pay upon written notice all reasonable charges, as additional rent, associated
with said removal. A single two-yard capacity dumpster is hereby authorized for the disposal of trash, providing that the location
of said receptacle is approved by LESSOR and LESSEE agrees to have said container provided and serviced at its expense by whichever
disposal firm may from time to time be designated by LESSOR. LESSOR approves the two storage containers and the cement storage
unit constructed in the parking lot.

 

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33. ENVIRONMENT

 

LESSEE will so conduct and operate the Leased
Premises as not to interfere in any way with the use and enjoyment of other portions of the same or neighboring buildings by others
by reason of odors, smells, noise, vibration, pets accumulation of garbage or trash, vermin or other pests, or otherwise, and will
at its expense employ a professional pest control service if necessary. LESSEE agrees to maintain efficient and effective devices
for preventing damage to heating equipment from harmful solvents, degreasers, cutting oils, etc. which may be used within the Leased
Premises. No hazardous waste or chemical waste, other than those set forth in Exhibit “C” attached hereto, shall be
used, generated, stored, disposed of or allowed to remain within the leased premises or the property at any time, and the LESSEE
shall be solely responsible for any and all corrosion or other damages associated with the improper use, generation, storage, and
control of the same by the LESSEE. The LESSEE agrees that it shall be solely and exclusively responsible for obtaining all appropriate
Federal, State and Local Permits for the handling and disposal of such waste and shall indemnify, reimburse and hold the LESSOR
harmless for any damages, actions, causes of actions, attorney's fees or any other costs incurred should such hazardous waste spill
on the property of the LESSOR. LESSOR shall be notified of the existence and conditions of all Local, State and Federal Permits,
as well as any changes of permit status.

 

34. RESPONSIBILITY

 

LESSOR shall not be held liable to anyone
for loss or damage caused in any way by the use, leakage, seepage or escape of water from any source, or for the cessation of any
service rendered customarily to the Property, or agreed to by the terms of this Lease, due to any accident, to the making of repairs,
alterations or improvements, to labor shortages or disputes, weather conditions, or mechanical breakdowns, to trouble or scarcity
in obtaining fuel, electricity, service or supplies from the sources from which they are usually obtained for the Property, or
to any cause beyond LESSOR's immediate control.

 

35. SURRENDER

 

LESSEE shall at the expiration or other
termination of this Lease remove all of the LESSEE's goods and effects from the Leased Premises. LESSEE shall deliver to LESSOR
the Leased Premises and all keys, access control cards (if used in the Building) locks, and other fixtures and equipment connected
therewith, and all alterations, additions and improvements made to or upon the Leased Premises, including but not limited to any
offices, partitions, floor coverings (including computer floors), window shades and blinds, plumbing and plumbing fixtures, air
conditioning equipment and duct work of any type, exhaust fans or heaters, water coolers, burglar alarms, telephone wiring, telephone
equipment (excluding telephone handsets and switching equipment), wooden or metal shelving which has been bolted, welded or otherwise
attached to the Building, air or gas distribution piping, compressors, overhead cranes, hoists, trolleys or conveyors, counters
or signs attached to walls or floors, and all electrical work, including but not limited to lighting fixtures of any type, wiring,
conduit, EMT, distribution panels, bus ducts, raceways, outlets and disconnects, unless otherwise directed by LESSOR in writing.
LESSEE shall deliver the Leased Premises broom clean and in the same condition as they were at commencement of the Lease Term,
or as they were put in during the Lease Term, reasonable wear and tear and damage by fire or other casualty only accepted. In the
event of LESSEE's failure to remove any of LESSEE's property from the Leased Premises, LESSOR is hereby authorized, without liability
to LESSEE for loss or damage thereto, and at the sole risk of LESSEE, to remove and store any such property at LESSEE's expense,
or to retain same under LESSOR's control, or to sell at public or private sale (without notice), any or all of the property not
so removed and to apply the net proceeds of such sale to the payment of any sum due hereunder, or to destroy such property which
shall be conclusively deemed to have been abandoned. In no case shall the Leased Premises be deemed surrendered to LESSOR until
the expiration date provided herein or such other date as may be specified in a written agreement between the parties and attached
hereto.

 

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36. LEGAL

 

In case LESSOR shall be made party to any
litigation commenced by or against LESSEE or by or against any parties in possession of the Leased Premises or any party thereof
claiming under LESSEE, LESSEE shall pay, as additional rent, all costs, including without limitation reasonable counsel fees incurred
by or imposed upon LESSOR in connection with such litigation, and shall also pay, as additional rent, all such costs and fees incurred
by LESSOR in connection with the enforcement by LESSOR of any obligations of LESSEE under this Lease. LESSEE shall defend, save
harmless and indemnify LESSOR from any liability or injury, loss, accident or damage to any person or property, and from any claims,
actions, proceedings and expenses and costs in connection therewith (including without limitation reasonable counsel fees) (i)
arising from the omission, fault, willful act, negligence or other misconduct of LESSEE or from any use made or thing done or occurring
on the Leased Premises not due to the omission, fault, willful act, negligence or other misconduct of LESSOR or (ii) resulting
from the failure of LESSEE to perform and discharge its covenants and obligations under this Lease.

 

37. GENERAL

 

(a) The invalidity or unenforceability of
any provision of this Lease shall not affect or render invalid or unenforceable any other provision hereof.

 

(b) The obligations of this Lease shall
run with the land, and this Lease shall be binding upon and inure to the benefit of the parties hereto and their respective successors
and assigns, except that LESSOR shall be liable only for obligations occurring before the beginning of the Lease Term, or thereafter
while owner of the entire Property.

 

(c) If LESSOR is acting under any trust
or corporation the obligations of LESSOR shall be binding upon the trust, estate or corporation, but not upon any trustee, officer,
corporate officer, shareholder, or beneficiary of the trust or corporation individually.

 

(d) This Lease is made and delivered in
the state of Massachusetts, and shall be interpreted, construed, and enforced in accordance with the laws thereof.

 

(e) This Lease was the result of negotiations
between parties of equal bargaining strength, and when executed by both parties shall constitute the entire agreement between said
parties. NO other oral or written representation shall have any effect hereon, and this agreement may not be altered, extended
or amended except by written agreement attached hereto or as otherwise provided herein.

 

(f) Notwithstanding any other statements
herein, LESSOR makes no warranty, express or implied, concerning the suitability of the Leased Premises for LESSEE's intended use.

 

(g) LESSEE agrees that if LESSOR does not
deliver possession of the Leased Premises as herein provided, LESSOR shall not be liable for any damages to LESSEE for such failure,
but LESSOR agrees to use reasonable efforts to obtain possession for LESSEE on or before the lease Commencement Date, as it may
be extended pursuant to the provisions of this Lease.

 

(h) LESSOR shall have the right to issue
to LESSEEs including LESSEE, and from time to time to revise, reasonable written Rules and Regulations pertaining to the Property,
and LESSEE shall upon receipt of said Rules and Regulations, and any revision(s) thereof, abide by same.

 

38. WAIVERS, ETC

 

No consent of waiver, express or implied,
by LESSOR, to or of any breach of any covenant, condition or duty of LESSEE shall be construed as a consent or waiver to or of
any other breach of the same or any other covenant, condition or duty. If LESSEE is several persons or a partnership LESSEE's obligations
are joint and also several.

 

    	15

    	 

    

 

39. OPTION TO EXTEND

 

On the conditions (which conditions LESSOR
may waive, at its election, by written notice to LESSEE at any time) that LESSEE is not in default of its covenants and obligations
under the Lease beyond applicable notice and cure periods, both as of the time of exercise of the Option to Extend, as hereinafter
defined, and at the commencement of the Extension Period, as hereinafter defined, then LESSEE shall have the right to extend the
term hereof (the “Option to Extend”) for one additional term of five years, ending on March 31, 2019 (the “Extension
Period’), to commence immediately upon the expiration of the then current term.

 

LESSEE may exercise such Option to Extend
by giving written notice to LESSOR (the “Extension Notice”) on or before the date which no less than twelve (12) months
prior to the expiration of the then current Term. Such Extension Period shall be upon the same terms and conditions of this Lease,
except that the Base Rent payable shall be set at the then fair market effective rent for the Leased Premises. In no event, however,
shall the Base Rent be less than the then-current Base Rent at the expiration of the current Term. For the purpose of this Section,
fair market effective rent shall mean the Base Rent plus such additional financial terms in the nature of rent and rent adjustments
customarily then being included in leases for similar space within the greater Waltham area. LESSEE shall, during the Extension
Period, continue to pay its proportionate share of LESSOR’s Real Estate Taxes and Operating Costs. Said fair market effective
rent for the Leased Premises shall be agreed upon by LESSOR and LESSEE; provided, however, if LESSOR and LESSEE are unable to agree
on said fair market effective rent within thirty (30) days of the date of the Extension Notice, said fair market effective rent
shall be conclusively determined by three (3) appraisers. Within fifteen (15) days of the expiration of such thirty (30) day period,
LESSOR and LESSEE shall each select an appraiser, who shall select a third. Should the two appraisers fail to agree on a third
within fifteen (15) days of the date on which such appraisers have been appointed, or if either LESSOR or LESSEE shall fail to
appoint an appraiser within the time provided, such appraiser shall be appointed by the American Institute of Appraisers. Each
party shall bear the cost of the appraiser selected by such party, and the cost of the third appraiser shall be shared equally
by LESSOR and LESSEE. If the three appraisers are unable to agree upon such fair market effective rent within fifteen (15) days
of the appointment of the third appraiser, the fair market effective rent shall be that determined by the appraiser not selected
by either LESSOR or LESSEE.

 

40. CERTIFICATE

 

If the LESSEE is a corporation, each of
the persons executing this instrument on behalf of the LESSEE, hereby covenants and warrants that the LESSEE is a duly existing
and valid corporation and that the LESSEE is qualified to do business in Massachusetts. Further, if the LESSEE is a corporation,
the LESSEE shall deliver to the LESSOR, at the time of execution of this Lease, a Clerk's or Secretary's Certificate in the form
attached hereto as Exhibit “D” (or other suitable form satisfactory to counsel for the LESSOR), as to the due authorization
of the execution of this Lease and incumbency of the signing officer.

 

IN WITNESS WHEREOF, LESSOR AND LESSEE have
hereunto set their hands and seals and intend to be legally bound hereby this 14th day of May, 2008.

 

	LESSOR:	 	LESSEE:
	 	 	 	 
	ATLANTIC-WALTHAM INVESTMENTS II, LLC	 	TECOGEN INC.
	By Its Agent,	 	 	 
	Atlantic Management Corporation	 	 	 
	By:	/s/ David Capobianco	 	By:	 /s/ Robert A. Panora 
	David Capobianco	 	Robert A. Panora
	Managing Partner	 	President
	 	 	 	 	 

 

    	16

    	 

    

 

LOADING DOCK CERTIFICATE

 

The Lessor and LESSEE hereby agree and certify
to one another the following condition/damage with respect to the premises.

 

LOADING DOCK(S):

 

1.

 

2.

 

3.

 

	LESSOR: ATLANTIC-WALTHAM INVESTMENT II, LLC
	 	 
	By Its Agent,	 
	Atlantic Management Corporation	 
	By:	/s/ David Capobianco	 
	David Capobianco	 
	Managing Partner	 
	 	 
	LESSEE: TECOGEN INC.	 
	 	 
	By:	/s/ Robert A. Panora	 
	Robert A. Panora	 
	President	 
	 	 	 

 

    	17

    	 

    

 

EXHIBIT A

 

DESCRIPTION OF PROPERTY

 

Parcel I - 45 First Avenue, Waltham, Massachusetts

 

The land with the buildings thereon and
all equipment and fixtures now or hereafter thereon

which are, or can by agreement of the parties be made a part
of the realty, situated in Waltham, Middlesex County, Massachusetts, shown on a Plan entitled “Plan of Land in Waltham, Mass.”
dated July 18, 1956, recorded with a deed from Gerald W. Blakeley et al. Trustees, to Crucible Center Company in Middlesex South
District, Deeds, Book 8785, Page 573, bounded and described as follows:

 

		SOUTHEASTERLY	by the Northwesterly Side Line of First Avenue, three hundred sixty-seven feet;

 

		SOUTHWESTERLY	by land of Blakeley, et al., two hundred ninety-five
feet;

 

		NORTHWESTERLY	by land now or formerly of Thomas I. Griggs, three hundred sixty-seven feet; and

 

		NORTHEASTERLY	by the parcel of land shown on said Plan as containing 130,000 square feet, two hundred ninety-five feet.

 

Containing 108,265 square feet of land.

 

Subject to and with the benefit of easements
and restrictions of record, if any, insofar as the same are now in force and applicable.

 

For title to Parcel I, see deed from Peter
Van and Champe A. Fisher, as Trustees under a Declaration of Trust made by Lillian Benjamin and Abram Berkowitz dated January 5,
1968, as amended, to Thermo Electron Corporation and recorded with the Middlesex County (Southern District) Registry of Deeds at
Book 16046, Page 94.

 

    	18

    	 

    

 

EXHIBIT B

 

DATA CERTIFICATE

 

The Lessor and LESSEE hereby agree and certify
to one another the following:

 

1. The Commencement Date of the lease is
April 1, 2009.

 

2. The Expiration Date of the original term
of this lease is March 31, 2014.

 

	LESSOR: ATLANTIC-WALTHAM INVESTMENT II, LLC
	 	 
	By Its Agent,	 
	Atlantic Management Corporation	 
	By:	/s/ David Capobianco	 
	David Capobianco	 
	Managing Partner	 
	 	 
	LESSEE: TECOGEN INC.	 
	 	 
	By:	/s/ Robert A. Panora	 
	Robert A. Panora	 
	President	 
	 	 	 

 

    	19

    	 

    

 

EXHIBIT C

 

LIST OF HAZARDOUS WASTES USED AT THE
PREMISES

 

The Company does not dispose any hazardous
wastes at the premises.

 

    	20

    	 

    

 

EXHIBIT D

 

CLERK'S CERTIFICATE

 

I, Anthony S. Loumidis Clerk of TECOGEN
INC., hereby certify that a meeting of the Board of Directors of said Corporation duly held at the offices of the Corporation,
held on February 13, 2008, at which meeting a quorum of the Directors was present and voting throughout approval was given for
the Corporation, as LESSEE, to enter into a Lease with ATLANTIC-WALTHAM INVESTMENT II, LLC, Lessor, for approximately 43,000 square
feet of space at 45 First Avenue, Waltham, Massachusetts, and said Lease to be for a term of five (5) years at a rent of (see *
below) Dollars per year, as adjusted, a copy of which Lease is hereto attached and made a part hereof.

 

I further certify that, Robert A. Panora,
President of the Corporation has authority to execute and deliver to the Lessor the Lease on behalf of the Corporation upon the
above terms.

 

WITNESS my hand and seal of the Corporation,
this 14th day May, 2008.

 

	 	 
	(Affix Corporate Seal)	

Annual Base (Fixed) Rent for the Lease Term:

		Years1-2:	43,000 s.f X $10.50/s.f = $451,500.00 per year or $37,625.00
per month

		Year3-5:	43,000 s.f X $11.50/s.f = $494,500.00 per year or $41,208.33
per month

 

    	21

    	 

    

 

EXHIBIT E

 

OPERATING EXPENSES

 

		·	Schedule of estimated 2009 annual operating expenses

 

		·	Real estate taxes for 2008

 

    	22

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