KNOXVILLE, Tenn. (AP) — The Tennessee Valley Authority says its chief operating officer will retire at the end of the year.

Chip Pardee joined TVA in April 2013. According to a Monday news release, Pardee’s contributions include improvements to the power generation fleet and the operations team. The utility says those improvements are helping it cut pollution from its plants and keep rates low while also providing reliable energy to customers.

TVA says Pardee will work with President and CEO Bill Johnson to transition Pardee’s responsibilities over the coming months. The utility did not immediately say when it expects to hire a replacement.

TVA is the nation’s largest public utility. It serves about 9 million people in parts of Alabama, Georgia, Kentucky, Mississippi, North Carolina, Tennessee and Virginia.