Exhibit 5.1


                                April 27, 2005

Pinnacle West Capital Corporation
400 North Fifth Street
Phoenix, Arizona 85004

Ladies and Gentlemen:

      We have acted as counsel to Pinnacle West Capital Corporation, an Arizona
corporation (the "Company"), in connection with the Company's preparation of the
registration statement on Form S-3, No. 333-121510 filed with the Securities and
Exchange Commission (the "Commission") by the Company on December 21, 2004 and
declared effective by the Commission on January 7, 2005 and the registration
statement on Form S-3, No. 333-101457 filed with the Commission by the Company
on November 25, 2002 and declared effective by the Commission on December 5,
2002 (collectively, the "Registration Statements"). The Registration Statements
relate to the issuance and sale from time to time, pursuant to Rule 415 of the
General Rules and Regulations (the "Rules") promulgated under the Securities Act
of 1933, as amended (the "Securities Act"), of common stock, no par value, of
the Company ("Common Stock") and other securities. We have also acted as counsel
to the Company in connection with the offering and sale of 5,300,000 shares (the
"Firm Shares"), pursuant to the Underwriting Agreement dated April 27, 2005 (the
"Underwriting Agreement") between the Company and the underwriters named therein
(the "Underwriters"), and, at the election of the Underwriters, up to 795,000
additional shares (the "Optional Shares" and together with the Firm Shares, the
"Offered Shares").

      This opinion is delivered in accordance with the requirements of Item
601(b)(5) of Regulation S-K under the Securities Act. We have examined (i) the
Registration Statements; (ii) the definitive prospectus, dated January 7, 2005
(the "Definitive Prospectus"), and the prospectus supplement dated April 27,
2005 (the "Prospectus Supplement") (such Definitive Prospectus, Prospectus
Supplement, and all material incorporated therein by reference being hereinafter
referred to as the "Prospectus"), relating to the Offered Shares; (iii) the
Amended and Restated Articles of Incorporation of the Company, as currently in
effect; (iv) the Bylaws of the Company as currently in effect; (v) the
resolutions adopted by the Board of Directors of the Company and by the Special
Committee of the Board of Directors of the Company relating to the filing of the
Registration Statements and the offering and sale of the Offered Shares; and
(vi) the Underwriting Agreement. We have also examined originals or copies,
certified or otherwise identified to our satisfaction, of such records of the
Company and such agreements, certificates of public officials, certificates of
officers or other representatives of the Company and others,



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April 27, 2005
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and such other documents, certificates and records as we have deemed necessary
or appropriate as a basis for the opinions set forth herein.

      Based upon the foregoing and in reliance thereon, and subject to the
qualifications and limitations set forth herein, we are of the opinion that,
upon the issuance and delivery of the Offered Shares in accordance with the
Underwriting Agreement and receipt by the Company of the consideration therefor
set forth in the Prospectus, and further assuming that the Offered Shares have
been duly authenticated, executed, countersigned, registered and delivered upon
payment therefor, the Offered Shares will be duly authorized, validly issued,
fully paid and nonassessable.

      We do not express any opinion as to the laws of any jurisdiction other
than the laws of the State of Arizona and the laws of the United States of
America. This opinion is limited to the laws, including the rules and
regulations thereunder, as in effect on the date hereof. We disclaim any
obligation to advise you of any change in any of these sources of law or
subsequent legal or factual developments which might affect any matters or
opinions set forth herein.

      We hereby consent to the filing of this opinion with the Commission as an
exhibit to the Registration Statements and the reference to our firm under the
heading "Legal Matters" in the Prospectus Supplement and under the heading
"Legal Opinions" in the Definitive Prospectus.

                                Very truly yours,

                               Snell & Wilmer LLP