UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March 31, 2005

     Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

     o Written communications pursuant to Rule 425 under the Securities Act (17CFR 230.425)

     o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

     o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

     o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

     This combined Form 8-K is separately filed by Pinnacle West Capital Corporation and Arizona Public Service Company. Each registrant is filing on its own behalf all of the information contained in this Form 8-K that relates to such registrant. Neither registrant is filing any information that does not relate to such registrant, and therefore makes no representation as to any such information.

GLOSSARY

ACC – Arizona Corporation Commission

APS – Arizona Public Service Company, a subsidiary of the Company

Company – Pinnacle West Capital Corporation

FERC – Federal Energy Regulatory Commission

kWh – kilowatt hour, one thousand watts per hour

January Form 8-K – Pinnacle West’s Current Report on Form 8-K filed on January 28, 2005

March Form 8-K – Pinnacle West’s Current Report on Form 8-K filed on March 29, 2005

Native Load – retail and wholesale sales supplied under traditional cost-based rate regulation

Pinnacle West – Pinnacle West Capital Corporation

Pinnacle West Energy – Pinnacle West Energy Corporation, a subsidiary of the Company

PWEC Dedicated Assets – the following Pinnacle West Energy Corporation power plants: Redhawk Units 1 and 2, West Phoenix Units 4 and 5 and Saguaro Unit 3

Sundance Plant – a 450-megawatt generating facility located approximately 55 miles southeast of Phoenix, Arizona

2004 Form 10-K – the Pinnacle West/APS Annual Report on Form 10-K for the fiscal year ended December 31, 2004

2004 Settlement Agreement – an agreement that, as approved by the ACC, established terms to resolve APS’ general rate case originally filed with the ACC in June 2003

TABLE OF CONTENTS

Item 2.02. Results of Operations and Financial Condition

     Certain of the Information referenced in Item 7.01 below relates to Pinnacle West’s results of operations for its fiscal quarter ended March 31, 2005. This Information is attached hereto as Exhibits 99.2, 99.3, and 99.7.

     On April 26, 2005, the Company issued a press release regarding its financial results for its fiscal quarter year ended March 31, 2005. A copy of the press release is attached hereto as Exhibit 99.9.

     The information being furnished pursuant to this Item 2.02 and in Exhibits 99.2, 99.3, 99.7, 99.9 and 99.10 of this report relating to the Company’s financial results for its fiscal quarter ended March 31, 2005 shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) or otherwise subject to the liabilities of that Section, and shall not be incorporated by reference into any registration statement or other document filed under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.

Item 7.01. Regulation FD Disclosure

Financial and Business Information

     The Company is providing quarterly consolidated statistical summaries, earnings variance explanations, and a glossary of relevant terms (collectively, “Information”) to help interested parties better understand its business (see Exhibits 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, and 99.8). This Information is concurrently being posted to the Company’s website at www.pinnaclewest.com. The Information may not represent all of the factors that could affect the Company’s operating or financial results for various periods. Some of the Information is preliminary in nature and could be subject to significant adjustment. Some of the Information is based on information received from third parties and may contain inaccuracies. The Company is not responsible for any such inaccuracies. Although the Company may update or correct the Information if it is aware that such Information has been revised or is inaccurate, the Company assumes no obligation to update or correct the Information and reserves the right to discontinue the provision of all or any portion of the Information at any time or to change the type of Information provided.

Earnings Outlook

     We currently estimate that 2005 earnings will be within a reasonable range around $3.00 per diluted common share. This estimate is based on a number of factors and assumptions, including but not limited to:

     Except as described in the following sentence, earnings per share amounts for the factors and assumptions discussed above are after income taxes and are based on diluted common shares outstanding before the expected equity issuance. Earnings per share amounts for the net effect of the expected equity issuance are after income taxes and are based on expected average common shares outstanding after the issuance.

     This earnings guidance supersedes all previous earnings guidance provided by the Company and is forward-looking information. Actual results may differ materially from our expectations. See “Forward-Looking Statements” below.

Silverhawk Power Station

     Pinnacle West, through its subsidiary Pinnacle West Energy, has a 75% ownership interest in Silverhawk, a 570 MW combined cycle power plant located 20 miles north of Las Vegas, Nevada. Silverhawk is the only Pinnacle West generating facility that operates as a fully competitive merchant generator. While we believe that our Silverhawk ownership interest will be profitable in the longer term, we estimate that in 2005 and 2006 it will incur annual after-tax losses in the range of $19 million to $23 million, or $0.20 to $0.25 per share. Such a loss for 2005 was assumed in developing the Company’s 2005 earnings outlook discussed above.

     Recently, we have received proposals from several parties that have expressed interest in acquiring our ownership interest in Silverhawk. These proposals contemplate a transaction closing in 2005. Such a transaction would result in our recognizing a loss. If such a transaction were to

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occur, we would plan to invest the after-tax sale proceeds, estimated to be in the range of $200 million to $215 million, into APS. No assurance can be given that the transaction will occur.

     The information being furnished pursuant to this Item 7.01 and in Exhibits 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7 and 99.8 shall not be deemed to be “filed” for purposes of Section 18 of the Exchange Act or otherwise subject to the liabilities of that Section.

Forward-Looking Statements

     This Report on Form 8-K contains forward-looking statements based on current expectations, and we assume no obligation to update these statements or make any further statements on any of these issues, except as required by applicable law. Forward-looking statements are often identified by words such as “estimate,” “predicts,” “hope,” “may,” “believe,” “should, ” “anticipate,” “plan,” “expect,” “require,” “intend,” “assume” and similar words. Because actual results may differ materially from expectations, we caution readers not to place undue reliance on these statements. A number of factors could cause future results to differ materially from historical results, or from results or outcomes currently expected or sought by us. These factors include, but are not limited to:

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Item 9.01. Financial Statements and Exhibits

     (c) Exhibits.

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SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, each registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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