Exhibit
10.1

     

    REVOLVING
LINE OF CREDIT AGREEMENT

    


    This
Revolving Line of Credit Agreement (the “Agreement”) is made and entered into in
this 17th day of December, 2009 by and between John Hatsopoulos (“Lender”),
residing at 3 Woodcock Lane, Lincoln, Massachusetts 01773 and American DG Energy
Inc., a corporation organized under the laws of Delaware (“Borrower”), with
offices located at 45 First Avenue, Waltham, Massachusetts 02451.

    


    In
consideration of the mutual covenants and agreements contained herein, the
parties agree as follows:

    


    
      	
               
      

            	
              1.

            	
              LINE
      OF CREDIT. During the term hereof, the Lender will from time to time, at
      the written request of the Borrower, lend to the Borrower such funds as
      may from time to time be requested by the Borrower (the “Credit Line”).
      The aggregate principal amount of such funds outstanding at any time shall
      not exceed Five Million U.S. Dollars ($5,000,000.00) (the “Credit Limit”).
      At the time of the first advance of funds under this Agreement, the
      Borrower shall execute and deliver to Lender the Promissory Note in the
      form attached to this Agreement. All sums advanced on the Credit Line or
      pursuant to the terms of this Agreement (each an “Advance”) shall become
      part of the principal of said Promissory
Note.

            


    

    


    
      	
               
      

            	
              2.

            	
              INTEREST.
      All sums advanced pursuant to this Agreement shall bear interest from the
      date each Advance is made until paid in full at the Bank Prime Rate as
      quoted from time to time in the Wall Street Journal plus one and one half
      percent (1.5%) per annum (the “Effective
Rate”).

            


    

    


    
      	
               
      

            	
              3.

            	
              TERM.
      The term of this Agreement shall commence as of the date first set forth
      above and shall terminate on December 31, 2012 (the “Maturity
      Date”).

            


    

    


    
      	
               
      

            	
              4.

            	
              ADVANCES.
      Any request for an Advance may be made from time to time and in such
      amounts as Borrower may choose; provided, however, any requested Advance
      will not, when added to the outstanding principal balance of all previous
      Advances, exceed the Credit Limit. Requests for Advances may be made
      orally or in writing by such officer of Borrower authorized by it to
      request such Advances. Until such time as Lender may be notified
      otherwise, Borrower hereby authorizes its President or Chief Financial
      Officer to request Advances. Lender shall transfer the amount of any
      Advance requested by Borrower in accordance with this Agreement
      unless  an event of default has occurred and is continuing
      hereunder either at the time of a request for an Advance or the date the
      Advance is to be made, or if an event has occurred or condition exists
      which, with the giving of notice or passing of time or both, would
      constitute an event of default hereunder as of such dates. Borrower shall
      use all funds loaned by Lender hereunder in connection with Borrower’s
      business.

            


    

    


    
      	
               
      

            	
              5.

            	
              REPAYMENT.
      Borrower shall pay accrued interest on the outstanding principal balance
      on a quarterly basis, in arrears, commencing at the end of each calendar
      quarter during which an Advance has been made or remains outstanding and
      unpaid, and continuing every quarter thereafter until the balance due
      hereunder is paid in full. The entire unpaid principal balance, together
      with any accrued interest and other unpaid charges or fees hereunder,
      shall be due and payable on the Maturity Date. All payments shall be made
      to Lender at such place as Lender designates from time to time. All
      payments received hereunder shall be applied first to any costs or
      expenses incurred by Lender in collecting such payment or to any other
      unpaid charges or expenses due hereunder; second to accrued interest; and
      third to principal. Borrower may prepay principal at any time without
      penalty.

            


    

    


    
      	
               
      

            	
              6.

            	
              SECURITY.  Borrower
      shall grant to Lender a first priority security interest in accounts
      receivable of Borrower relating to projects or contracts entered into on
      or after the date of any Advance hereunder in an amount equal to not less
      than One Hundred and Ten Percent (110%) of the amount of the aggregate
      outstanding and unpaid Advances plus any accrued and unpaid interest with
      respect to such Advances. Borrower shall execute and deliver any
      agreements and documents reasonably requested by Lender to effectuate the
      grant and perfection of security interests in accounts receivable referred
      to above.

            


    

     

    
      
         

      

      
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              7.

            	
              REPRESENTATIONS
      AND WARRANTIES. In order to induce Lender to enter into this Agreement and
      to make the advances provided for herein, Borrower represents and warrants
      to Lender as follows:

            


    

    


    
      	
               
      

            	
              a.

            	
              Borrower
      is duly organized, validly existing, and in good standing under the laws
      of the State of Delaware with the power to own its assets and to transact
      business in Massachusetts, and in such other states where its business is
      conducted.

            


    

    


    
      	
               
      

            	
              b.

            	
              Borrower
      has the authority and power to execute and deliver any document required
      hereunder and to perform any condition or obligation imposed under the
      terms of such documents.

            


    

    


    
      	
               
      

            	
              c.

            	
              The
      execution, delivery and performance of this Agreement and each document
      incident hereto will not violate any provision of any applicable law,
      regulation, order, judgment, decree, article of incorporation, by-law,
      indenture, contract, agreement, or other undertaking to which Borrower is
      a party, or which purports to be binding on Borrower or its assets, and
      will not result in the creation or imposition of a lien on any of its
      assets.

            


    

    


    
      	
               
      

            	
              d.

            	
              There
      is no action, suit, investigation, or proceeding pending or, to the
      knowledge of Borrower, threatened, against or affecting Borrower or any of
      its assets which, if adversely determined, would have a material adverse
      affect on the financial condition of Borrower or the operation of its
      business.

            


    

    


    
      	
               
      

            	
              8.

            	
              EVENTS
      OF DEFAULT. An event of default will occur if any of the following events
      occurs:

            


    

    


    
      	
               
      

            	
              a.

            	
              Borrower’s
      failure to pay any principal or interest hereunder within ten (10) days
      after the same becomes due.

            


    

    


    
      	
               
      

            	
              b.

            	
              Any
      representation or warranty made by Borrower in this Agreement or in
      connection with any borrowing or request for an Advance hereunder, or in
      any certificate, financial statement, or other statement furnished by
      Borrower to Lender is untrue in any material respect at the time when
      made.

            


    

    


    
      	
               
      

            	
              c.

            	
              Default
      by Borrower in the observance or performance of any other covenant or
      agreement contained in this
Agreement.

            


    

    


    
      	
               
      

            	
              d.

            	
              Filing
      by Borrower of a voluntary petition in bankruptcy seeking reorganization,
      arrangement or readjustment of debts, or any other relief under the
      Bankruptcy Code as amended or under any other insolvency act or law, state
      or federal, now or hereafter
existing.

            


    

    


    
      	
               
      

            	
              e.

            	
              Filing
      of an involuntary petition against Borrower in bankruptcy seeking
      reorganization, arrangement or readjustment of debts, or any other relief
      under the Bankruptcy Code as amended, or under any other insolvency act or
      law, state or federal, now or hereafter existing, and the continuance
      thereof for sixty (60) days undismissed, unbonded, or
      undischarged.

            


    

    


    
      
      

    

    
      
      

    

    
      	
               
      

            	
              9.

            	
              REMEDIES.
      Upon the occurrence of an event of default as defined above, Lender may
      (i) declare the entire unpaid principal balance, together with accrued
      interest thereon, to be immediately due and payable without presentment,
      demand, protest, or other notice of any kind, and (ii)  suspend
      or terminate any obligation that Lender may have hereunder to make
      additional Advances. To the extent permitted by law, Borrower waives any
      rights to presentment, demand, protest, or notice of any kind in
      connection with this Agreement. No failure or delay on the part of Lender
      in exercising any right, power, or privilege hereunder will preclude any
      other or further exercise thereof or the exercise of any other right,
      power, or privilege. The rights and remedies provided herein are
      cumulative and not exclusive of any other rights or remedies provided at
      law or in equity. Borrower agrees to pay all costs of collection incurred
      by reason of the default, including court costs and reasonable attorney's
      fees.

            


    

     

    
      
         

      

      
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              10.

            	
              NOTICE.
      Any notices or other communications required or permitted under this
      Agreement shall be sufficiently given if delivered personally, sent by
      registered or certified mail, postage prepaid, or sent by Federal Express
      or similar courier service to the other party at its address first set
      forth above or at such other address as either party may specify by
      written notice to the other party. Unless otherwise specified herein, such
      notices or other communications shall be deemed received (a) on the date
      delivered, if delivered personally; (b) three business days after being
      sent, if sent by registered or certified mail; or (c) the next business
      day, if delivered by Federal Express or similar courier
      service.

            


    

    


    
      	
            	
              11.

            	
              GOVERNING
      LAW. This Agreement shall be governed by and construed in accordance with
      the laws (other than the conflict of laws rules) of the Commonwealth of
      Massachusetts.

            


    

    


    
      	
            	
              12.

            	
              TITLES
      AND CAPTIONS. All section titles or captions contained in this Agreement
      are for convenience only and shall not be deemed part of the context nor
      affect the interpretation of this
Agreement.

            


    

    


    
      	
            	
              13.

            	
              ENTIRE
      AGREEMENT. This Agreement contains the entire understanding between and
      among the parties and supersedes any prior understandings and agreements
      among them respecting the subject matter of this
  Agreement.

            


    

    


    
      	
            	
              14.

            	
              AGREEMENT
      BINDING. This Agreement shall be binding upon the heirs, executors,
      administrators, successors and assigns of the parties
    hereto.

            


    

    


    
      	
            	
              15.

            	
              FURTHER
      ACTION. The parties hereto shall execute and deliver all documents,
      provide all information and take or forbear from all such action as may be
      necessary or appropriate to achieve the purposes of the
      Agreement.

            


    

    


    
      	
            	
              16.

            	
              PARTIES
      IN INTEREST.  Nothing herein shall be construed to be to the
      benefit of any third party, nor is it intended that any provision shall be
      for the benefit of any third party.

            


    

    


    IN
WITNESS WHEREOF, the undersigned have executed this Revolving Line of Credit
Agreement as of the day and year first set forth above.


    


    
      
        
          
            
              	
                      LENDER:

                    	 	
                      BORROWER:

                    
	 
      	 	 
      
	 
      	 	
                      AMERICAN
      DG ENERGY INC.

                    
	 
      	 	 
      
	
                       

                    	 	
                      By:
      

                    	
                       

                    
	
                      Name:
      John N. Hatsopoulos

                    	 	
                      Name:

                    	
                      Anthony
      S. Loumidis

                    
	 
      	 	
                      Title:

                    	
                      Chief
      Financial
Officer

                    


            

          

        

      

    

     

    
      
         

      

      
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    AMERICAN
DG ENERGY INC.

    PROMISSORY
NOTE

    


    
      
        
          	
                  U.S.
      $_______________

                	
                  _____________,
      2010             
      

                


        

      

    

     

    FOR VALUE
RECEIVED, American DG Energy Inc., a corporation organized under the laws of
Delaware (“Borrower”), with offices located at 45 First Avenue, Waltham,
Massachusetts 02451, agrees to pay to John N. Hatsopoulos
(“Lender”), residing at 3 Woodcock Lane, Lincoln, Massachusetts 01773, or
order, the principal sum of ______________ U.S. Dollars ($_____________), on demand,
together with interest from the date hereof on the unpaid principal balance at
the rate specified below, until repaid in full. Prepayment of principal,
together with accrued interest, may be made at any time without penalty.
Interest hereon shall accrue from the date hereof at the Bank Prime Rate as
quoted from time to time in the Wall Street Journal plus one and one half
percent (1.5%) per annum. Accrued interest shall be due and payable quarterly in
arrears on the last day of each calendar quarter.

    


    In the
event that any amount of principal hereof, or (to the extent permitted by
applicable law) any interest hereon or any other amount payable hereunder is not
paid in full when due (whether as scheduled, on demand, by acceleration or
otherwise), Borrower shall pay interest (after as well as before entry of
judgment thereon to the extent permitted by law) on such unpaid amount to
Lender, from the date such amount becomes due until the date such amount is paid
in full, payable on demand of Lender at a rate per annum equal at all times to
12% per annum (the “Default Rate”). Additionally, and without limiting the
foregoing, following the occurrence and during the continuance of any Event of
Default (as defined below), at the option of Lender, the interest rate shall be
the Default Rate. Such interest on overdue amounts shall be payable on demand.
All computations of interest shall be made on the basis of a year of 360 days
for the actual number of days (including the first day but excluding the last
day) occurring in the period for which such interest is payable. Each
determination by Lender of any applicable rate of interest, and of any change
therein, in the absence of manifest error shall be conclusive and binding on the
parties hereto.

    


    Payment
shall be made in lawful tender of the United States unconditionally in full
without set-off, counterclaim or, to the extent permitted by applicable law,
other defense, all of which rights of Borrower are hereby expressly waived by
Borrower. All payments hereunder shall be made to Lender at Lender’s address set
forth above (or to such other place as Lender shall designate in a written
notice to Borrower), and, unless Borrower has obtained Lender’s written consent
to another form of payment, such payment shall be made by wire transfer of
immediately available funds by no later than 12:00 noon (Boston time) on the due
date of the payment, in accordance with Lender’s payment
instructions.

    


    Whenever
any payment hereunder shall be stated to be due, or whenever any interest
payment date or any other date specified hereunder would otherwise occur, on a
day other than a Business Day (as defined below), then such payment shall be
made, and such interest payment date or other date shall occur, on the next
succeeding Business Day, and such extension of time shall in such case be
included in the computation of payment of interest hereunder. As used herein,
“Business Day” means a day (i) other than Saturday or Sunday, and (ii) on which
commercial banks are open for business in Boston, Massachusetts.

    


    Borrower
represents and warrants to Lender that:

    


    (i)           Organization and
Powers. Borrower is a corporation duly organized, validly existing and in
good standing under the laws of the State of Delaware, and has all requisite
power and authority to own its assets and carry on its business and to execute,
deliver and perform its obligations under this Note.

    


    (ii)          Authorization; No
Conflict. The execution, delivery and performance by Borrower of this
Note have been duly authorized by all necessary corporate action of Borrower and
do not and will not (A) contravene the terms of the organizational
documents of Borrower; or (B) result in a breach of or constitute a default
under any material lease, instrument, contract or other agreement to which
Borrower is a party or by which it or its properties may be bound or affected;
or (C) violate any provision of any law, rule, regulation, order, judgment,
decree or the like binding on or affecting Borrower.

     

    
      
         

      

      
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    (iii)         Binding Obligations.
This Note constitutes the legal, valid and binding obligation of Borrower,
enforceable against Borrower in accordance with its terms.

    


    (iv)         Consents. No
authorization, consent, approval, license, exemption of, or filing or
registration with, any governmental authority or agency, or approval or consent
of any other person or entity is required for the due execution, delivery or
performance by Borrower of this Note.

    


    Any of
the following events which shall occur shall constitute an “Event of
Default”:

    


    (a)          Payments. Borrower
shall fail to pay when due any amount of principal hereof, or interest hereon or
other amount payable hereunder, and such failure shall continue unremedied for
five (5) days.

    


    (b)          Representations and
Warranties. Any representation or warranty by Borrower under or in
connection with this Note shall prove to have been incorrect in any material
respect when made or deemed made.

    


    (c)          Insolvency. (i)
Borrower shall (A) admit in writing its inability to, or shall fail
generally or be generally unable to, pay its debts (including its payrolls) as
such debts become due, (B) make a general assignment for the benefit of
creditors, (C) be dissolved, liquidated, wound up or cease its corporate
existence, or (D) commence any voluntary proceeding or case seeking to
adjudicate it a bankrupt or insolvent, or seeking reorganization, arrangement,
adjustment, intervention, suspension of payments, or composition of it or its
debt under any law relating to bankruptcy, insolvency, suspension of payments or
reorganization or relief of debtors, or seeking appointment of a receiver,
trustee, intervenor or liquidator, or other similar official for it or for any
substantial part of its property, (ii) an involuntary proceeding or case
shall be commenced against Borrower seeking any of the foregoing relief and
remain undismissed for a period of 30 days; (iii) an order for relief or
other order or adjudication shall be entered against Borrower under any such
bankruptcy, insolvency or similar law; (iv) any receiver, trustee, or other
official or Person shall be appointed to take possession of any property of
Borrower; or (v) Borrower shall take any corporate action to authorize, or
shall consent to, any of the actions or events set forth above in this
paragraph.

    


    If any
Event of Default shall occur and be continuing, Lender may, by notice to
Borrower, declare the entire unpaid principal amount of this Note, all interest
accrued and unpaid hereon and all other amounts due hereunder to be forthwith
due and payable, whereupon the principal hereof, all such accrued interest and
all such other amounts shall become and be forthwith due and payable, without
presentment, demand, protest or further notice of any kind, all of which are
hereby expressly waived by Borrower, provided that if an event described in
paragraph (c) above shall occur, the result which would otherwise occur only
upon giving of notice by Lender to Borrower as specified above shall occur
automatically, without the giving of any such notice.

    


    Borrower
agrees to pay on demand the costs and expenses of Lender, and fees and
disbursements of counsel, in connection with any Event of Default, the
enforcement or attempted enforcement of, and preservation of any rights or
interests under, this Note, and any out-of-court workout or other refinancing or
restructuring or any bankruptcy or insolvency case or proceeding.

    


    No single
or partial exercise of any power under this Note shall preclude any other or
further exercise of such power or exercise of any other power. No delay or
omission on the part of Lender in exercising any right under this Note shall
operate as a waiver of such right or any other right thereunder.

     

    
      
         

      

      
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    All
notices and other communications provided for hereunder shall, unless otherwise
stated herein, be in writing and mailed, sent or delivered to the respective
parties hereto at or to their respective addresses set forth herein, or at or to
such other address as shall be designated by any party in a written notice to
the other party hereto.  All such notices and communications shall be
effective: (i) if delivered by hand, when delivered; (ii) if sent by
overnight courier service, when delivered; and (iii) if sent by mail, upon
the earlier of the date of receipt or five Business Days after deposit in the
mail, first class (or air mail, with respect to communications to be sent to or
from the United States), postage prepaid.

    


    This Note
shall be binding on Borrower and its successors and assigns, and shall be
binding upon and inure to the benefit of Lender, any future holder of this Note
and their respective successors and assigns. Borrower may not assign or transfer
this Note or any of its obligations hereunder without Lender’s prior written
consent.

    


    This Note
shall be governed by and construed in accordance with the laws of the
Commonwealth of Massachusetts.

    


    Borrower
hereby (a) submits to the non-exclusive jurisdiction of the courts of the
Commonwealth of Massachusetts and the Federal courts of the United States
sitting in the District of Massachusetts (collectively, the “Massachusetts
Courts”), for the purpose of any action or proceeding arising out of or relating
to this Note, (b) irrevocably waives (to the extent permitted by applicable
law) any objection which it now or hereafter may have to the laying of venue of
any such action or proceeding brought in any of the Massachusetts Courts, and
any objection on the ground that any such action or proceeding in any
Massachusetts Court has been brought in an inconvenient forum, and
(c) agrees that (to the extent permitted by applicable law) a final
judgment in any such action or proceeding brought in a Massachusetts Court shall
be conclusive and may be enforced in other jurisdictions by suit on the judgment
or in any other manner permitted by law.

    


    IN
WITNESS WHEREOF, Borrower signing below by its duly authorized legal
representative(s) has executed this Note as of the date first above
mentioned.


    


    AMERICAN
DG ENERGY INC.


    


    
      
        
          
            	
                    By:

                  	
                     

                  	 
	
                    Name:

                  	
                    Anthony
      S. Loumidis

                  	 
	
                    Title:

                  	
                    Chief
      Financial Officer

                  	 


          

        

      

    

     

    
      
         

      

      
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