LETTERHEAD OF LEBOEUF, LAMB, GREENE & MACRAE, L.L.P.



                                              March 6, 1998



Public Service Company of Colorado
1225 17th Street
Denver, Colorado 80202

Ladies and Gentlemen:

          We have acted as counsel for Public Service Company of Colorado, a
Colorado corporation (the "Company"), and PSCO Capital Trust I, a statutory
business trust created under the Business Trust Act of the State of Delaware
(the "Trust"), in connection with the preparation and filing with the Securities
and Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended (the "Securities Act"), of a Registration Statement on Form S-3 (the
"Registration Statement"), relating to the following securities of the Company:
(i) first collateral trust bonds (the "Bonds"); (ii) unsecured senior debt
securities (the "Senior Debt Securities"); and (iii) unsecured subordinated debt
securities (the "Subordinated Debt Securities", and together with the Bonds and
the Senior Debt Securities, the "Debt Securities").  The Registration Statement
also relates to the preferred securities of the Trust (the "Preferred
Securities") and the guarantee of the Preferred Securities by the Company to the
extent described in the Prospectus forming a part of the Registration Statement
(the "Guarantee", and together with the Debt Securities and the Preferred
Securities, the "Offered Securities").  The Offered Securities will be issued
from time to time pursuant to the provisions of Rule 415 under the Securities
Act.

          The Preferred Securities will be issued pursuant to an Amended and
Restated Declaration of Trust, the form of which is filed as an exhibit to the
Registration Statement.  The Bonds will be issued in one or more series under an
Indenture dated as of October 1, 1993 the ("Bond Indenture"), between the
Company and First Trust of New York, National Association, as successor trustee
thereunder (the "Bond Trustee").  The Senior Debt Securities will be issued in
one or more series pursuant to an Indenture (the "Senior Indenture") between the
Company and The Bank of New York, as trustee (the "Senior Trustee"), the form of
which 



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is filed as an exhibit to the Registration Statement.  The Subordinated Debt 
Securities will be issued in one or more series pursuant to an Indenture (the 
"Subordinated Indenture") between the Company and The Bank of New York, as 
trustee (the "Subordinated Trustee"), the form of which is filed as an exhibit 
to the Registration Statement.  The Guarantee of the Preferred Securities is 
to be issued pursuant to the Preferred Securities Guarantee Agreement (the 
"Preferred Securities Guarantee") between the Company and The Bank of New York 
(the "Guarantee Trustee"), the form of which is filed as an exhibit to the 
Registration Statement.

          As such counsel, we have examined and relied upon a copy of the
Registration Statement.  We have also examined such corporate records,
certificates and other documents as we have considered necessary for the
purposes of this opinion.  In such examination, we have assumed the genuineness
of all signatures, the authenticity of all documents submitted to us as
originals, the conformity to the original documents of all documents submitted
to us as copies and the authenticity of the original of such latter documents. 
As to any facts material to our opinion, we have, when relevant facts were not
independently established, relied upon the aforesaid records, certificates and
documents.

          Based on the foregoing examination, and subject to the qualifications
and limitations contained herein, we are of the opinion that:

          1.   when (i) the Registration Statement, as finally amended
     (including any necessary post-effective amendments), shall have become
     effective under the Securities Act and the Senior Indenture and the
     Subordinated Indenture, including any necessary supplemental indentures,
     filed as exhibits to the Registration Statement shall have been duly
     qualified under the Trust Indenture Act of 1939, as amended (the "Trust
     Indenture Act"); (ii) all orders, consents or other authorizations of the
     Colorado Public Utilities Commission (the "CPUC") required for the valid
     issuance and sale of a particular series of Bonds, Senior Debt Securities
     or Subordinated Debt Securities, as applicable, have been obtained; and
     (iii) a prospectus supplement with respect to a particular series of Debt
     Securities shall have been filed with the Commission in compliance with the
     Securities Act and the rules and regulations thereunder, no further
     authorization, consent or approval by any regulatory authority will be
     required for the valid issuance and sale of the Debt Securities of such
     series.

          2.   when (i) the Senior Indenture and the Subordinated Indenture
     shall have been duly executed and delivered by the Company and the Senior
     Trustee and the Subordinated Trustee, respectively; and (ii) a Board
     Resolution or Officer's Certificate within the meaning of the Bond
     Indenture, Senior Indenture or Subordinated Indenture, as the case may be,
     shall have been issued or a supplemental indenture entered into, in



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     accordance with the Bond Indenture, Senior Indenture or Subordinated
     Indenture, as the case may be, detailing the establishment of a particular
     series of Debt Securities, such series of Debt Securities shall have been
     duly authorized by the Company.

          3.   upon the execution and filing with the Bond Trustee, the Senior
     Trustee and the Subordinated Trustee, as applicable, of the proper papers
     with respect to the Bonds, Senior Debt Securities or Subordinated Debt
     Securities, as applicable, of a particular series, the Debt Securities of
     such series shall be issuable under the terms of the Bond Indenture, Senior
     Indenture or Subordinated Indenture, as applicable.

          4.   when such series of Debt Securities shall have been duly
     executed, authenticated and delivered in accordance with the corporate and
     governmental authorizations and the instruments referred to above and the
     purchase price for such series of Debt Securities has been received by the
     Company, the Debt Securities of such series will be legally issued and
     binding obligations of the Company and will be entitled to the benefits of
     the Bond Indenture, Senior Indenture or Subordinated Indenture, as
     applicable, on a parity with the securities of other series which may be
     hereafter issued thereunder pursuant to the terms of such indenture (except
     as may be limited by applicable bankruptcy, insolvency, reorganization,
     moratorium, fraudulent transfer or other similar laws affecting the
     enforcement of creditors' rights generally and by the effect of general
     principles of equity, regardless of whether considered in a proceeding in
     equity or at law).

          5.   when (i) the Registration Statement, as finally amended
     (including any necessary post-effective amendments), shall have become
     effective under the Securities Act and the Preferred Securities Guarantee
     shall have been duly qualified under the Trust Indenture Act; (ii) all
     orders, consents or other authorizations of the CPUC required for the
     performance of the Preferred Securities Guarantee have been obtained; and
     (iii) a prospectus supplement with respect to the Preferred Securities
     Guarantee and the Preferred Securities shall have been filed with the
     Commission in compliance with the Securities Act and the rules and
     regulations thereunder, no further authorization, consent or approval by
     any regulatory authority will be required with respect to the performance
     by the Company of its obligations with respect to the Preferred Securities
     Guarantee.

          6.   when (i) the Preferred Securities Guarantee shall have been duly
     executed and delivered by the Company and the Guarantee Trustee; and (ii)
     the Preferred Securities have been duly issued and sold and the purchase
     price therefor has been received by the Trust in the manner contemplated by
     the Registration Statement, 



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     the Preferred Securities Guarantee will constitute a valid and binding 
     obligation of the Company (except as may be limited by applicable 
     bankruptcy, insolvency, reorganization, moratorium, fraudulent transfer or 
     other similar laws affecting the enforcement of creditors' rights generally
     and by the effect of general principles of equity, regardless of whether 
     considered in a proceeding in equity or at law).

          We do not find it necessary for the purposes of this opinion to cover,
and accordingly we express no opinion as to, the application of the securities
or blue sky laws of the several states to the sale of the securities to be
registered pursuant to the Registration Statement.  Without limiting the
generality of the foregoing, we express no opinion in connection with the
matters contemplated by the Registration Statement, and no opinion may be
implied or inferred, except as expressly set forth herein.

          Our opinion expressed above is limited to the laws of the State of New
York and the State of Colorado, and the federal laws of the United States of
America.

          We hereby consent to the filing of this opinion letter as an exhibit
to the Registration Statement and the use of our name under the headings
"Description of the New Bonds," "Description of the 1939 Mortgage" and "Validity
of the Securities" in the Prospectus forming a part of the Registration
Statement and in any amendments or supplements to the Registration Statement and
Prospectus.


                                   Very truly yours,

                                   /s/ LeBoeuf, Lamb, Greene & MacRae
                                                  L.L.P.