Bill Post, chief executive of Pinnacle West Capital Corp., the parent company of Arizona Public Service, will retire on April 30 after 38 years with the company.
Post said he will remain as a member of the company's board of directors.
Pinnacle West and APS President Don Brandt was named to succeed Post as Pinnacle West's chief executive and chairman of the board.
Don Robinson, current senior vice president of planning and administration, will become president and chief operating officer of APS.
Director Cathy Munro said the moves were consistent with a succession plan that had been developed in the executive office.
"The board greatly respects the important contributions that Bill Post has made to the company and the community," she said.
Post, 58, joined APS in 1971 as a draftsman in metro operations. He became an officer in 1982, advancing to president and chief operating officer of APS in 1995. He was named chairman of the board and chief executive of both companies in February 2001.
His tenure was marked by enormous growth in the number of APS customers and rapid expansion of the company's renewable energy programs. But the company also faced operating problems at the Palo Verde Nuclear Generating Station. A Palo Verde performance-improvement program was launched in 2007 under the supervision of the U.S. Nuclear Regulatory Commission.
Also higher prices for fuel and equipment caused the company to seek several electricity rate increases from the Arizona Corporation Commission in the past few years. Another increase is pending before the regulatory panel.
In a letter to employees, Post said APS prices are only 11 percent higher than in 1995, one-fourth the overall rate of inflation.
Brandt, 54, joined APS and Pinnacle West as chief financial officer in 2002 and was promoted to president of APS in 2007. Prior to joining the Phoenix company he was senior vice president of Ameren Corp., a St. Louis-based energy services company.