Sipics, 58, headed the subsidiary of PPL Corp. that delivers electricity to 1.
3 million Pennsylvania customers. He was responsible for storm response and repairing outages of all sorts.
William H. Spence, executive vice president and chief operating officer of PPL Corp., will replace Sipics while the company decides on a permanent successor.
"His (Sipics) exhaustive knowledge of both the company and the wider utility industry has been essential to the success of PPL, especially in the last decade," said James H. Miller, who last year succeeded Bill Hecht as chairman, president and CEO of PPL Corp.
Sipics joined PPL in 1970 as an engineer in the system planning department. In 1998, he became the first head of PPL's unregulated energy marketing subsidiary, which is now PPL EnergyPlus.