SecProbe.io

January 18, 2012
 Via E-mail

John N. Hatsopoulos Chief Executive Officer Tecogen Inc. 45 First Avenue Waltham, MA 02451
Re: Tecogen Inc.
Registration Statement on Form S-1 Filed December 22, 2011
  File No. 333-178697

Dear Mr. Hatsopoulos:

We have reviewed your registration statem ent and have the following comments.  In
some of our comments, we may ask you to provi de us with information so we may better
understand your disclosure.
 Please respond to this letter by amending your registration statement and providing the
requested information.  If you do not believe  our comments apply to your facts and
circumstances or do not believe an amendment is appropriate, please tell us why in your
response.
 After reviewing any amendment to your re gistration statement and the information you
provide in response to these comments, we may have additional comments.
 Registration Statement on Form S-1

 General

1. We note that you are proposing to register the resale of up to 35,381,768 shares of your
common stock on behalf of certain selling stockholders listed in the registration
statement.  Given the size of this offering relative to the number of outstanding shares
held by non-affiliates, as well as the nature of  the selling stockholders, we believe this
transaction might be a primary offering.  Pleas e provide us with your analysis as to why
this offering is a secondary offering under Rule  415(a)(1)(i) and not an indirect primary
offering for which the selling stockholders should  be identified as underwriters.  In your
analysis, you may wish to  address the following fact ors: how long the selling
stockholders have held the securities, the ci rcumstances under which they received them,
their relationship to the registrant, the amount  of securities involve d, whether they are in
the business of underwriting securities, and fi nally, whether under all the circumstances it

John N. Hatsopoulos Tecogen Inc. January 18, 2012 Page 2

 appears that they are acting as a conduit for the company.  Please refer to Question
612.09 of the Division’s Compliance & Disclosu re Interpretations for Securities Act
Rules.
 Prospectus Cover Page

2. We note your statement that the selling stockhol ders do not include any of your directors,
officers or 10% holders and the prospectus ma y not be used by any such person or entity.
Given that John N. Hatsopoulos  and George N. Hatsopoulos  are selling stockholders,
please delete this statement.
 Table of Contents

3. Please remove the last sentence of the third paragraph on the prospe ctus cover page and
the last two sentences of the first paragraph under the table of contents.  These statements
may suggest to investors that you are not re sponsible for omissions of material facts
necessary to make your statements  not misleading at the time of sale or contract of sale.
Information that is conveyed afte r the time of sale or contract  of sale is not taken into
account for purposes of section 12(a)(2) or  17(a)(2) of the Se curities Act.  See  Securities
Act Rule 159.
Prospectus Summary, page 1

4. Please ensure that your summary is balance d.  Please disclose up front that you have
incurred operating losses for your prior fiscal  years, including quantifying the number of
years that you have had such losses, and th at you expect you will continue to incur such
losses.
5. We note certain statements regarding the be nefits of your CHP pr oducts, including that
such products decrease greenhouse gas emissions and that you have a proven track record of reliability in commercial CHP systems.  Please provide additional disclosure supporting such statements, including how your products reduce greenhouse gas
emissions (or, if, alternatively, these system s have lower emissions than other competing
products) and examples of your proven track record.
6. We note your disclosure on page 10 that your internal controls ove r financial reporting
were not effective as of September 30, 2011. Pl ease prominently disclose this in your
Summary section.

7. We note your disclosure on page 59 that John N. Hatsopoulos, your CEO, spends only
approximately 20% of his business time on th e affairs of the company.  Please disclose
this fact in your Summary section.

John N. Hatsopoulos Tecogen Inc. January 18, 2012 Page 3

 8. We note that you conduct a notable amount of  business and other transactions with
certain “affiliated companies,” and that a number of members of management and the
Board also have positions with such affiliated companies.  Please provide an overview of your relationship with such affiliated companies in your Summary section.
 Risk Factors, page 4

 General

9. We note in the introductory paragraph to your  risk factors secti on you state that there
may be risks that you do not consider materi al now but may become material, or there
may be risks that you have not yet identified. You must disclose all risks that you believe
are material at this time. Delete this language from your  introductory paragraph.

10. We note that many of your risk  factors are currently written as if you are an early stage
company without any significant operating history.  For exam ple, we note that you state
that you may not be successful in executing your business plan, that you expect
competition for your products and services, a nd that businesses and consumers might not
adopt cogeneration solutions as a means for obt aining their power need s.  These are just
examples. However, we note that your co mpany has actually been operating since the
early 1960’s, and some members of management have been with the company since the
sale of Tecogen in 2000, or prio r thereto.  Please comprehensiv ely revise your risk factors
to ensure that each of them reflects the cu rrent state of your business and explains the
specific risk as applied to the specific facts and circum stances of your company.

11. In general, risk factors that  describe circumstances that could apply equally to other
businesses that are similarly situated are gene ric risks that should not  be included in your
risk factor section. For example, we note that  the following risk factors appear to contain
generic disclosure:

 Our success is dependent upon attracting and retaining highly qualified personnel
. . .,(page 6);

 We may make acquisitions th at could harm our financial performance, (page 9);

 Our ability to access capital for the repayment of debts . . ., (page 9);

 Our quarterly operating results are subject  to fluctuations . . ., (page 9); and

These are just examples. Please either eliminat e these generic risks, or revise them to
state the specific material ri sks that apply to you or to th e purchasers in this offering.

12. We note that your risk factors often cite a specific risk wit hout providing any examples of
how that risk has specifically impacted your business so that investors may have a better

John N. Hatsopoulos Tecogen Inc. January 18, 2012 Page 4

 understanding of how this risk could imp act your future operations and financial
condition.  We note the following examples:
 The execution of our growth strategy is dependent upon the continued availability
of third-party financing . . ., page 4;

 We are dependent on third-part y suppliers . . ., page 5;

 Business and consumers might not adopt cogeneration solutions as a means for
obtaining their electricity and power needs, page 6;

 We operate in a highly regulated bu siness environment . . ., page 7;

 Utility companies or governmental entities could place barriers to our entry into
the marketplace . . ., page 7;

 Commodity market factors impact our costs . . ., page 8;

 Our products involve a lengthy sales cycle and we may not anticipate sales levels
appropriately . . ., page 8;

 The economic viability of our projects de pends on the price spread between fuel
and electricity . . ., page 8; and

 We are exposed to credit risks with respect to some of our customers (page 9).
 These are just examples.  Please revise accordingly.
 We may be unable to fund our future  operating requirements . . ., page 4

13. Please revise this risk factor to address whether your curren t funds are sufficient to fund
your operating requirements.
 We are controlled by a small group of majority stockholders…, page 10

14. Please reconcile this risk f actor with the fact that Ge orge and John Hotsopoulos are
seeking to sell 100% of their holdings and in clude a risk factor addressing the potential
risks related to these individua ls having little or no contin uing stake in the company.
 Selling Security Holders, page 14

15. Please disclose how the selling security hol ders acquired the securities they may offer
and sell pursuant to the registration statement,  including the dates of the transactions, the
number of shares purchased in each tr ansaction, and the purch ase price, if any.

John N. Hatsopoulos Tecogen Inc. January 18, 2012 Page 5

 Legal Matters, page 21

16. We note that the disclosure under the h eading “Legal Matters ” relates to legal
proceedings.  It is unclear why this disclosure  has been included in this section.  Please
revise to advise who will opine on the valid ity of the common stock offered pursuant to
the registration statement.
 Business, page 22

 General

17. We note your disclosure that the company wa s formed in the early 1960s, and was then
sold to private investors in 2000.  Howeve r, your disclosure throughout the business
section and the prospectus does not, at times, seem consistent with a company that has
been in operation for an extended period of time.   Please revise your disclosure to provide
investors with a better unde rstanding of the general de velopment of your business,
including, for example, how long you have sold  your current products  and whether there
have been any significant changes in the focu s of your business since its establishment in
the 1960s.  Please also disclose whether you r company was known as Tecogen prior to
2000, or was instead a part of Thermo El ectron at that time.  Please make any
corresponding changes to the Summary section as well.

18. We note that your disclosure includes various  qualitative and compar ative statements and
that for certain of these statements, you ha ve provided footnotes citing the sources of
such information.  Please delete  these footnotes and instead indicate in the text of your
disclosure both the name and date of the source for the various statements.  Finally,
please tell us whether you commissioned the re port or any part thereof and, if so, please
either file consents or explai n to us why you are not required  to do so under Rule 436 of
Regulation C and Section 7 of the Securities Ac t.  To expedite our review, please provide
us with copies of each source, clearly mark ed to highlight the portion or section that
contains this information and cross-reference it  to the appropriate loca tion in your filing.

19. Please disclose whether you are attempting to  incorporate the information on external
web sites into this prospectus.  Please s ee our Use of Electronic Media, Interpretive
Release No. 33–7856 (Apr. 28, 2000) for further gui dance regarding the use of hyperlinks
in your prospectus.
20. We note that you provide data relating to the e fficiency of the electr icity industry and the
prospective CHP market in various sectors, in cluding an estimate of  market potential, but
this data is from 2000 and 2004.  If you wish to provide this sort of data to investors,
please ensure that it takes into account more recent developments.  The disclosure should
not include data that has since changed or is no longer accurate given developments in
the industry in the past decade.  Please revise accordingly.

John N. Hatsopoulos Tecogen Inc. January 18, 2012 Page 6

 21. We note your use of industry and product sp ecific jargon throughout this section.  For
example, you use the terms “UL-certifie d,” “inverter,” “conv entional induction
generators,” and “permanent-magnet generato r.”  Please revise to provide context for
these terms so an investor not familiar w ith your industry can understand such terms.

22. Please revise your disclosure  to include the following:

 The sources and availability of raw materials, and the names of principal
suppliers; and

 An estimate of the amount spent during each of the last two fiscal years on
research and development activities, and if applicable, the extent to which the cost
of such activities is born e directly by customers.
 See
 Item 101(h)(4) of Regulation S-K.

23. Please include a discussion of your dependen ce on one or a few major customers. We
note in particular the disclosure in Note 13 to  the financials on pa ge F-36 that you receive
a significant portion of your revenues from  sales to American DG Energy Inc.  See  Item
101(h)(4)(vi) of Regulation S-K.
 Industry Background, page 23

24. Please provide illustrative support and context for certain of the statements that you make
in this section.  For example, please provide  additional disclosure as to how many large
industrial plants have ad opted CHP technology, and what you mean by “large” when
referring to such plants.  This is only an example.

25. We note the list of reasons why CHP acceptance in the commercial sector is increasing.
Please explain why these reasons increase CH P acceptance.  For example, you state that
CHP systems reduce pollutants more “easily, ch eaply and quickly” but it is unclear what
other systems you are comparing the CHP sy stems to in making such a comparison.
Please also clarify who you are referring to in your statement regarding the pressure to
cut “their” operating costs.  Further, it appe ars that this disclosu re should appear under
“Tecogen’s solution” as opposed to “Industry Background.”
26. We note your reference throughout this section to “grid congestion” and to “rigorous air
quality rules.”  Please provide a brief overview of the specifics of th e air quality rules and
grid congestion in the Industry Background section.
 Our Products and Services, page 24

27. Please revise your disclosure to explain the markets for each of your products and, to the
extent material to an underst anding of your business, please disclose the contribution to

John N. Hatsopoulos Tecogen Inc. January 18, 2012 Page 7

 your revenues made by each of these products.  Please also provide context so that an
investor may understand the extent of time th at you have sold each of these products and
the effect of each of these products  on your overall financial condition.

28. Please revise your disclosure to describe th e distribution methods of your products.  See

Item 101(h)(4)(ii) of Regulation S-K.
29. We note your statement that you have “recen tly” developed an advanced technology for
controlling engine emissions in conjuncti on with the California Energy Commission and
the Southern California Gas Company.  Pl ease disclose what you mean by recently.
Please also advise whether, other than with re gard to the sale of units to the Sacramento
Municipal Utility District in Californ ia in mid-2011, you have entered into any
agreements relating to the Ultra emission control produc t, including its sale or
development.  Please also file any such ag reements as exhibits to the registration
statement.  See
 Item 601(b)(10) of Regulation S-K.

30. We note that the engine used in your cogene ration modules and chil lers is supplied by
General Motors.  Please disc losure whether you purchase such motors pursuant to a
supply agreement with General Motors, or othe rwise.  Please also file any such supply
agreement or similar agreement as an exhibit to the registration statement.  See  Item
601(b)(10) of Regulation S-K.

31.  We note your disclosure on page 25 th at your cogeneration products offer many
compelling advantages, such as lower cost, better  quality control, higher reliability, etc.
Please revise your disclosure to specify thos e product