PNW

pnw-202602250000764622falseAZ00000072868-KFebruary 25, 2026falseAZfalsefalsefalsefalsefalse00007646222026-02-252026-02-250000764622pnw:ArizonaPublicServiceCompanyMember2026-02-252026-02-25

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

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): February 25, 2026

Commission File Number Exact Name of Each Registrant as specified in its charter; State of Incorporation; Address; and Telephone NumberIRS Employer Identification No.

1-8962 PINNACLE WEST CAPITAL CORPORATION86-0512431

(an Arizona corporation) 400 North Fifth Street, P.O. Box 53999 PhoenixArizona85072-3999 (602) 250-1000

1-4473 ARIZONA PUBLIC SERVICE COMPANY86-0011170

(an Arizona corporation) 400 North Fifth Street, P.O. Box 53999 PhoenixArizona85072-3999 (602)250-1000

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:

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

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

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

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

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol(s) Name of each exchange on which registered

Common Stock PNW New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

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

Item 2.02. Results of Operations and Financial Condition.

The following information is furnished pursuant to Item 2.02.

On February 25, 2026, Pinnacle West Capital Corporation (the “Company” or “Pinnacle West”) issued a press release regarding its financial results for the fiscal quarter and full year ended December 31, 2025 and its earnings outlook for 2026. A copy of the press release is attached hereto as Exhibit 99.1.

Item 7.01. Regulation FD Disclosure.

The following information is furnished pursuant to Item 7.01.

The Company is providing a copy of the slide presentation made in connection with its earnings conference call on February 25, 2026. This information contains Company operating results for the fiscal quarter and fiscal year ended December 31, 2025, earnings outlook for 2026, and a quarterly and full year consolidated statistical summary. The slide presentation is attached hereto as Exhibit 99.2 and is concurrently being posted to the Company’s website at www.pinnaclewest.com.

Item 9.01.    Financial Statements and Exhibits. (d)    Exhibits

Exhibit No.Registrant(s)Description

99.1Pinnacle West APSEarnings News Release issued on February 25, 2026

99.2Pinnacle West APSPinnacle West Fourth Quarter and Full-Year 2025 Results slide presentation accompanying February 25, 2026 conference call

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.

PINNACLE WEST CAPITAL CORPORATION

(Registrant)

Dated: February 25, 2026By: /s/ Andrew Cooper Andrew Cooper Senior Vice President and Chief Financial Officer

ARIZONA PUBLIC SERVICE COMPANY

(Registrant)

Dated: February 25, 2026By: /s/ Andrew Cooper Andrew Cooper Senior Vice President and Chief Financial Officer

pnw-202511030000764622falseAZ00000072868-KNovember 3, 2025falseAZfalsefalsefalsefalsefalse00007646222025-11-032025-11-030000764622pnw:ArizonaPublicServiceCompanyMember2025-11-032025-11-03

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

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): November 3, 2025

Commission File Number Exact name of registrant as specified in its charter; State or other jurisdiction of incorporation or organization; Address of principal executive offices, including zip code; and Registrant's telephone number, including area codeIRS Employer Identification No.

1-8962 PINNACLE WEST CAPITAL CORPORATION86-0512431

(an Arizona corporation) 400 North Fifth Street, P.O. Box 53999 PhoenixArizona85072-3999 (602)250-1000

1-4473 ARIZONA PUBLIC SERVICE COMPANY86-0011170

(an Arizona corporation) 400 North Fifth Street, P.O. Box 53999 PhoenixArizona85072-3999 (602)250-1000 Not Applicable (Former name or former address, if changed since last report.)

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:

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

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

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

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

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol(s) Name of each exchange on which registered

Common Stock, no par value PNW New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

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

Item 2.02. Results of Operations and Financial Condition.

The following information is furnished pursuant to Item 2.02.

On November 3, 2025, Pinnacle West Capital Corporation (“Pinnacle West”) issued a press release regarding its financial results for the fiscal quarter ended September 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1.

Item 7.01. Regulation FD Disclosure.

The following information is furnished pursuant to Item 7.01.

Pinnacle West is providing a copy of the slide presentation made in connection with the quarterly earnings conference call on November 3, 2025. This information contains Pinnacle West operating results for the fiscal quarter ended September 30, 2025 and earnings outlook for 2025 and 2026. The slide presentation is attached hereto as Exhibit 99.2 and is concurrently being posted to Pinnacle West’s website at www.pinnaclewest.com.

Item 9.01.    Financial Statements and Exhibits.

(d)    Exhibits

Exhibit No.Registrant(s)Description

99.1Pinnacle West Arizona Public Service CompanyEarnings News Release issued on November 3, 2025

99.2Pinnacle West Arizona Public Service CompanyPinnacle West Capital Corporation Third Quarter 2025 Results slide presentation accompanying November 3, 2025 conference call

104.0Pinnacle West Arizona Public Service Company104 Cover Page Interactive Data File (embedded within the Inline XBRL document)

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.

PINNACLE WEST CAPITAL CORPORATION

(Registrant)

Dated: November 3, 2025By: /s/ Andrew Cooper Andrew Cooper Senior Vice President and Chief Financial Officer

ARIZONA PUBLIC SERVICE COMPANY

(Registrant)

Dated: November 3, 2025By: /s/ Andrew Cooper Andrew Cooper Senior Vice President and Chief Financial Officer

pnw-202508060000764622falseAZ00000072868-KAugust 6, 2025falseAZfalsefalsefalsefalsefalse00007646222025-08-062025-08-060000764622pnw:ArizonaPublicServiceCompanyMember2025-08-062025-08-06

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

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): August 6, 2025

Commission File Number Exact name of each registrant as specified in its charter; State or other jurisdiction of incorporation or organization; Address of principal executive offices, including zip code; and Registrant's telephone number, including area codeIRS Employer Identification No.

1-8962 PINNACLE WEST CAPITAL CORPORATION86-0512431

(an Arizona corporation) 400 North Fifth Street, P.O. Box 53999 PhoenixArizona85072-3999 (602)250-1000

1-4473 ARIZONA PUBLIC SERVICE COMPANY86-0011170

(an Arizona corporation) 400 North Fifth Street, P.O. Box 53999 PhoenixArizona85072-3999 (602)250-1000 Not Applicable (Former name or former address, if changed since last report.)

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:

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

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

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

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

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol(s) Name of each exchange on which registered

Common Stock, no par value PNW New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

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

Item 2.02. Results of Operations and Financial Condition.

The following information is furnished pursuant to Item 2.02.

On August 6, 2025, Pinnacle West Capital Corporation (“Pinnacle West”) issued a press release regarding its financial results for the fiscal quarter ended June 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1.

Item 7.01. Regulation FD Disclosure.

The following information is furnished pursuant to Item 7.01.

Pinnacle West is providing a copy of the slide presentation made in connection with the quarterly earnings conference call on August 6, 2025. This information contains Pinnacle West operating results for the fiscal quarter ended June 30, 2025 and earnings outlook for 2025. The slide presentation is attached hereto as Exhibit 99.2 and is concurrently being posted to Pinnacle West’s website at www.pinnaclewest.com.

Item 9.01.    Financial Statements and Exhibits.

(d)    Exhibits

Exhibit No.Registrant(s)Description

99.1Pinnacle West Arizona Public Service CompanyEarnings News Release issued on August 6, 2025

99.2Pinnacle West Arizona Public Service CompanyPinnacle West Capital Corporation Second Quarter 2025 Results slide presentation accompanying August 6, 2025 conference call

104.0Pinnacle West Arizona Public Service Company104 Cover Page Interactive Data File (embedded within the Inline XBRL document)

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.

PINNACLE WEST CAPITAL CORPORATION

(Registrant)

Dated: August 6, 2025By: /s/ Andrew Cooper Andrew Cooper Senior Vice President and Chief Financial Officer

ARIZONA PUBLIC SERVICE COMPANY

(Registrant)

Dated: August 6, 2025By: /s/ Andrew Cooper Andrew Cooper Senior Vice President and Chief Financial Officer