Tennessee Valley Authority engages in the production and sale of electricity in the United States. It generates power from coal-fired, nuclear, hydroelectric facilities, and combustion turbine and diesel generators. The company sells power at wholesale to distributor customers comprising municipalities and cooperatives that resell the power to their customers at a retail rate. It also supplies power directly to federal agencies and customers with large or unusual loads, as well as customers with whom it has entered into exchange power arrangements. As of September 30, 2008, it operated various power generating facilities, including 29 conventional hydroelectric sites, 1 pumped storage hydroelectric site, 11 coal-fired sites, 3 nuclear sites, 11 combustion turbine sites, 2 diesel generator sites, 1 wind energy site, 1 digester gas site, 1 biomass cofiring site, and 15 solar energy sites. The company supplies power in Tennessee, northern Alabama, northeastern Mississippi, and southwestern Kentucky and in portions of northern Georgia, western North Carolina, and southwestern Virginia to approximately nine million customers. It also manages the Tennessee River and its tributaries for various river-system purposes, such as navigation; flood damage reduction; power generation; environmental stewardship; shoreline use; and water supply for power plant operations, consumer use, recreation, and industry. The company was founded in 1931 and is based in Knoxville, Tennessee.