Exhibit 5.1

                                  July 2, 2003

Arizona Public Service Company
400 North 5th Street
Phoenix, Arizona 85004

Ladies and Gentlemen:

     Reference is made to (a) your proposed  offering of up to  $500,000,000  of
your debt securities  (the  "Securities"),  as contemplated by the  Registration
Statement (the "Registration  Statement") on Form S-3 to be filed by you on July
2, 2003, with the Securities and Exchange Commission under the Securities Act of
1933, as amended (the "Act");  and (b) any  registration  statement  registering
additional  Securities  pursuant to Rule  462(b) of the Act that  relates to the
Registration Statement (the "Rule 462(b) Registration Statement").

     We have examined originals or copies,  certified or otherwise identified to
our satisfaction,  of such corporate records, agreements, and other instruments,
certificates,   orders,   opinions,   correspondence   with  public   officials,
certificates provided by your officers and representatives,  and other documents
as we have deemed  necessary  or advisable  for the  purposes of  rendering  the
opinions set forth herein.

     Based on the foregoing,  it is our opinion that after (i) the  Registration
Statement, and the Rule 462(b) Registration Statement, if applicable, shall have
become effective, (ii) all required regulatory approvals have been obtained, and
(iii) you shall  have  entered  into one or more  underwriting  or  distribution
agreements  with  respect to the  Securities  then to be offered and the initial
public  offering price for each of such  Securities and the discounts  therefrom
and  commission  therefor  shall have been  determined in  accordance  with such
underwriting or distribution  agreements,  pursuant to the authorization of your
Board  of  Directors  and  the  applicable  order  of  the  Arizona  Corporation
Commission,  then,  when (i) the Securities  have been issued,  sold,  executed,
authenticated, and delivered, and (ii) the purchase price therefor has been paid
to you as  contemplated  in the  Registration  Statement  and  the  Rule  462(b)
Registration  Statement,  if applicable (including the Exhibits thereto), and in
any relevant  amendment  thereto or in any Rule 424 supplement to the prospectus
contained in the Registration  Statement;  the Securities will be validly issued
and will constitute legal,  valid, and binding  obligations of you except as the
same may be  limited  by (a)  general  principles  of equity  or by  bankruptcy,
insolvency, reorganization,  arrangement, moratorium, or other laws or equitable
principles  relating  to or  affecting  the  enforcement  of  creditors'  rights
generally,  or  by  equitable  principles  that  limit  the  right  to  specific
performance  or  otherwise  limit  remedial  action  or the  enforcement  of any
security  provided for the Securities,  and (b) the  qualification  that certain

Arizona Public Service Company
July 2, 2003
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waivers,  procedures,  remedies,  and other  provisions of the Securities may be
unenforceable under or limited by the law of the State of Arizona; however, such
law does not in our opinion  substantially  prevent the practical realization of
the benefits thereof.  In giving the above opinion, we have assumed that the law
of the jurisdiction or jurisdictions that govern the Securities is substantially
the same as the law of the State of Arizona.

     Consent  is  hereby  given  to the  use of  this  opinion  as  part  of the
Registration   Statement  and  the  Rule  462(b)  Registration   Statement,   if
applicable,  and to the use of our name wherever it appears in said Registration
Statement,  the related prospectus,  and the Rule 462(b) Registration Statement,
if applicable.

                                        Very truly yours,

                                        Snell & Wilmer L.L.P.