April 24, 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 March 7, 2019
           Response dated December 27, 2018
           File No. 001-34392

Dear Mr. Middleton:

       We have limited our review of your filing to the financial statements
and related
disclosures 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
September 5, 2018 letter.

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

Item 7. Management's Discussion and Analysis of Financial Condition and Results
of Operations
Contractual Obligations, page 39

1.    Please explain to us why your contractual obligations table does not
include your
      Convertible Senior Notes issued in March 2018. Refer to Item 303(a)(5) of
Regulation S-
      K. Revise future filings as appropriate.
 Paul B. Middleton
FirstName LastNamePaul B. Middleton
Plug Power Inc.
Comapany NamePlug Power Inc.
April 24, 2019
April 2 2019 Page 2
Page 24,
FirstName LastName
Consolidated Statements of Operations, page F-5

2.       We note your presentation of the line item "Interest and other
expense, net". Please
         provide to us detail of the significant individual components of this
line item and explain
         how you considered Item 5-03(b)(7)   (9) of Regulation S-X in your
presentation of a
         single net line item.
Note 1 - Nature of Operations
Liquidity, page F-10

3.       We note on page F-11 that in the third quarter of 2018 your master
lease agreement with
         Wells Fargo was amended ("Wells Fargo MLA"). You have accounted for
the amended
         agreement as a sale/leaseback and have concluded that the leaseback is
classified as an
         operating lease under ASC 842. To help us better understand your
application of ASC
         842, please respond to the following:

             Describe the modifications made to the Wells Fargo MLA in the
third quarter of
             2018.
             Describe how you concluded that the leaseback qualifies as an
operating lease and
             discuss the material assumptions used in your analysis of the
criteria in ASC 842-10-
             25-2.
             Describe how you concluded that the transfer of the assets was a
sale pursuant to ASC
             842-40-25-1 and ASC 842-40-25-2.
4.       With respect to the power purchase agreements ("PPA") with your
customers described
         on pages F-11 and F-14, tell us how you determined that the
arrangements qualify as
         operating leases. Include in your response the material assumptions
used in your analysis
         for each of the criteria in ASC 842-10-25-2.
Form 8-K filed March 7, 2019

Exhibit 99.1, page 1

5.       Please refer to comment 6 in our letter dated September 5, 2018. We
note throughout your
         earnings release you are presenting the non-GAAP measure, adjusted
EBITDA, with
         greater prominence than the most directly comparable GAAP measure. For
example, we
         note your references to adjusted EBITDA in the header, opening bullet
points and the first
         two paragraphs of your earnings release without any discussion or
presentation of the
         most directly comparable GAAP measure. Please revise your non-GAAP
presentations in
         future earnings releases to present the most directly comparable GAAP
measures with
         equal or greater prominence. Refer to Question 102.10 of the
Compliance and Disclosure
         Interpretations on Non-GAAP Financial Measures.
 Paul B. Middleton
FirstName LastNamePaul B. Middleton
Plug Power Inc.
Comapany NamePlug Power Inc.
April 24, 2019
Page 24,
April 3 2019 Page 3
FirstName LastName
6.       On page 5, you indicate that adjusted gross profit excludes the
interest component of
         operating leases associated with project financings. It appears this
is a calculated amount
         presented solely for the purpose of excluding it from this non-GAAP
measure. ASC Topic
         842 recognizes a single lease cost for operating leases on the basis
of the pattern in which
         the benefits conveyed by the lease are consumed. Please tell us how
you considered
         Question 100.04 of the Compliance and Disclosure Interpretations on
Non-GAAP
         Financial Measures in concluding that adjusted gross profit does not
constitute an
         individually tailored recognition method.
Reconciliation of Non-GAAP Financial Measures, page 12

7.       Please address the following regarding your presentation of adjusted
EBITDA:

             Clarify if management considers adjusted EBITDA a liquidity or
performance
             measure. Based on the reconciliation of this measure to net cash
(used by) provided
             by operating activities it appears that management considers this
a liquidity measure.
             However, in the second sentence of the Notes section you state
that management uses
             your non-GAAP measures as a basis for evaluating the company's
financial
             performance.
             Explain the purpose of this measure, how management uses it, what
it is intended to
             represent and why you believe it is useful to investors.
             Explain the purpose of the adjustments for changes in working
capital, cash based
             interest expense on corporate debt and restructuring and other
non-recurring charges.
             Explain the purpose of the adjustment for right of use asset
depreciation and interest
             associated with PPA financing. Clarify if this adjustment relates
to operating leases
             and/or finance leases and explain to us how this amount is
calculated.
        You may contact Eric Atallah at (202) 551-3663 or Kevin Kuhar,
Accounting Branch
Chief, at (202) 551-3662 if you have any questions.



                                                               Sincerely,

                                                               Division of
Corporation Finance
                                                               Office of
Electronics and Machinery