According to the U.S. Energy Information Administration, at the end of December 2020, the United States had 94 operational commercial nuclear reactors. These are based at 56 sites, and 28 states have a nuclear power plant, pumping thousands of megawatts of electricity into the grid every year. The U.S. has used nuclear-generated electricity since 1958, and its nuclear power plant fleet has an average age of 39 years. In 2016, the last new reactor came online in the country, the Watts Bar Unit 2 in 2016 in Tennessee.