EXHIBIT 5.1

Stephen E. Rounds, Attorney at Law
4635 East Eighteenth Ave.
Denver, Colorado 80220

January 10, 2000
OnLine Power Supply, Inc.
6909 S. Holly Circle
Suite 200
Englewood, Colorado 80112

Re:      Registration Statement on Form SB-2
         SEC File No. 333-93341

Gentlemen:

         OnLine  Power  Supply,  Inc.   ("Company")  has  filed  a  registration
statement for a rescission  offer by the Company to refund money (plus interest)
paid to the Company by certain  investors who bought shares of common stock, and
shares of series A and series B preferred  stock  (since  converted to shares of
common  stock,  as set  forth in the  registration  statement).  Hereafter,  the
securities which are the subject of the  registration  statement are referred to
as the "rescission shares." I have acted as counsel to the Company in connection
with the preparation and filing of the registration statement.

         Pursuant to the registration  statement,  when declared effective,  the
holders  of the  rescission  shares  will have the right to  either  accept  the
Company's  refund  offer,  or to decline  the offer and thereby  reaffirm  their
investment decision to keep all the rescission shares.

         My opinion and consent is required in connection with such registration
statement.  Such opinion and consent are to be filed as separate exhibits to the
pre-effective amendment no. 1 to the registration statement.

                               DOCUMENTS REVIEWED

         I have examined originals,  certified copies or other copies identified
to my satisfaction, of the following:

         1.       Articles of Incorporation of the Company.

         2. Bylaws of the Company.

         3. All exhibits listed in Part II of the registration statement on Form
            SB-2.

         4. Part I of the registration statement.

         5. Minutes of proceedings of the Company board of directors from August
            1996 to the date hereof.

         6. Other documents as appropriate under the circumstances.


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OnLine Power Supply, Inc.
January 10, 2000
Page -2-


         I have also consulted with officers and representatives of the Company,
and  received  such  representations  and  assurances  concerning  the  exhibits
described in paragraph 3 and the registration  statement  described in paragraph
4, as I have deemed advisable or necessary under the  circumstances.  Although I
have not  undertaken  independent  verification  of the matters  covered by this
paragraph,  I have no reason to believe that the  representations and assurances
received are materially inaccurate or false.

                                     OPINION

         The  following  opinion is subject to  compliance  by the Company  with
applicable  state  securities  laws,  to  declaration  of  effectiveness  of the
Company's  registration  statement,  and to the last sentence of this paragraph.
Based on my review of the  documents  listed  above,  it is my opinion  that the
shares of common  stock to be in effect  offered  and sold by the Company to the
holders of the rescission shares who do not elect to accept the Company's refund
offer,  will be upon such  effective  offer and sale to such  persons,  duly and
validly issued, fully paid and non-assessable  shares of the common stock of the
Company.  This opinion  assumes that the refund offer is conducted in accordance
with the final prospectus contained in the effective registration statement.

         No opinion is  expressed,  and none shall be inferred to be  expressed,
with  respect  to  federal  and state  income  tax laws and their  impact on the
holders of the rescission shares.

         No opinion is  expressed,  and none shall be inferred to be  expressed,
with  respect  to  the  financial   statements  contained  in  the  registration
statement.

         This  opinion  has  been  delivered  to you for the  purpose  of  being
included as an exhibit to the registration  statement and is intended solely for
your benefit.

Yours Sincerely,

 /s/   Stephen E. Rounds




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