CEO of Tennessee Valley Authority Tom Kilgore announced Thursday that he will retire within four to six months, according to the utility's Facebook page.
TVA officials could not be immediately reached for comment.
The announcement came during TVA's board of directors meeting Thursday in Knoxville.
Kilgore took over as chief executive officer in October 2006, according to TVA's website.
Before that, he served as president and chief operating officer.
He came to TVA from Progress Ventures, which is a subsidiary of Progress Energy, where he was CEO.
Kilgore had also served as CEO of Oglethorpe Power Corporation in Georgia.
Politicians started responding to the news Thursday afternoon.
U.S. Sen. Lamar Alexander, R-Tenn., said Kilgore helped lead TVA through challenging times.
"Now, the TVA board's job is to find a strong manager for its nuclear plants and clean air objectives, a manager who can ensure that TVA will continue to provide reliable electricity at a cost low enough to help create jobs in the Tennessee Valley," he said.
One of the most recent challenges Kilgore and the board faced is the Watts Bar Nuclear Unit 2 project, which was over budget and off-schedule.
TVA leaders asked for as much as $2 billion more to complete Watts Bar 2 and extended the timetable.
The project was originally set to be complete this year, but the new timetable extends through 2015.