January 7, 2000



Arizona Public Service Company
400 North Fifth Street
Phoenix, Arizona  85004

Ladies and Gentlemen:

     Reference is made to (a) your proposed  offering of up to $ 525,000,000  of
your securities (the  "Securities"),  as contemplated by the combined prospectus
contained in the Registration  Statement (the "Registration  Statement") on Form
S-3 to be filed by you on January  7, 2000,  with the  Securities  and  Exchange
Commission  under the  Securities  Act of 1933,  as amended (the  "Act"),  which
Securities  include (i) $ 500,000,000  of New Bonds,  Debt  Securities  (as such
terms are defined in the Registration Statement), or any combination thereof, to
be registered pursuant to the Registration  Statement,  and (ii) $ 25,000,000 of
New Bonds, Debt Securities,  or any combination thereof,  previously  registered
under Registration No. 333-58445; 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,  (b) the necessity for compliance with the
statutory  procedural  requirements  governing  the  exercise  of  remedies by a
secured creditor,  and (c) the qualification  that certain 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.

                                               Snell & Wilmer L.L.P.