June 20, 2019

Paul B. Middleton
Chief Financial Officer
Plug Power Inc.
968 Albany Shaker Road
Latham, NY 12110

       Re: Plug Power Inc.
           Form 10-K for the Fiscal Year Ended December 31, 2018
           Filed March 13, 2019
           Form 8-K filed May 8, 2019
           Response dated May 8, 2019
           File No. 001-34392

Dear Mr. Middleton:

       We have reviewed your May 8, 2019 response to our comment letter and
have the
following comments. In some of our comments, we may ask you to provide us with
information
so we may better understand your disclosure.

       Please respond to these comments within ten business days by providing
the requested
information or advise us as soon as possible when you will respond. If you do
not believe our
comments apply to your facts and circumstances, please tell us why in your
response.

       After reviewing your response to these comments, we may have additional
comments. Unless we note otherwise, our references to prior comments are to
comments in our
April 24, 2019 letter.

Form 10-K for Fiscal Year Ended December 31, 2018

Note 1 - Nature of Operations
Liquidity, page F-10

1.    We note your response to prior comment 3. Please describe to us the
specific terms of any
      renewal and purchase options contained in your agreement with Wells
Fargo, including
      the renewal periods, rates and exercise prices and how those rates and
prices are
      determined.
 Paul B. Middleton
FirstName LastNamePaul B. Middleton
Plug Power Inc.
Comapany NamePlug Power Inc.
June 20, 2019
Page 2
June 20, 2019 Page 2
FirstName LastName
2.       We further note in your response to prior comment 3 that the fair
value of the leased asset
         is based upon the sales price to the lessor in your sale/leaseback
transactions. Please tell
         us how you considered the fact that the sale price might be different
than the fair value of
         the asset and the paragraphs you relied upon in GAAP for your
conclusion. Refer to ASC
         842-40-30-1 and paragraph 361 in the Basis of Conclusions.
3.       We note your response to prior comment 4. Please describe to us the
specific terms of the
         renewal options contained in your PPA lease agreements, including
renewal periods and
         rates and how those rates are determined.
4.       We note from your response to prior comment 4 that you used an
incremental borrowing
         rate of two percent to determine the present value of the lease
payments in your PPAs.
         Please explain to us how you concluded it was appropriate to use an
incremental
         borrowing rate instead of the rate implicit in the lease. In your
response address the
         consideration you gave to ASC 842-10-25-4 and 842-30-30-1.
Form 8-K filed May 8, 2019

Exhibit 99.1, page 1

5.       We note from your response to comment 7 that you consider adjusted
EBITDA to be a
         liquidity measure. However, we note that you are excluding the cash
flow effects
         associated with changes in working capital from the measure, which
appears to be
         inconsistent with presenting a liquidity measure and may be
potentially misleading to
         investors. Please revise your non-GAAP presentation accordingly.
        You may contact Eric Atallah at (202) 551-3663 or Kevin Kuhar,
Accounting Branch
Chief, at (202) 551-3662 with any questions.



                                                               Sincerely,

                                                               Division of
Corporation Finance
                                                               Office of
Electronics and Machinery