The average annual capacity factor for United States nuclear power plants reached 91 percent in 2025, the highest figure of any generation type tracked by the Energy Information Administration.

As of March 2026 the country had 96 operating commercial reactors at 57 nuclear power plants spread across 28 states. Combined net summer generating capacity stood at 98,441 megawatts, and the average reactor age was about 44 years.

Illinois holds more reactors than any other state, with 11 units at six plants, and closed 2025 with the largest state nuclear capacity at roughly 11,592 megawatts. The Alvin W. Vogtle plant in Georgia is the largest single station in the country at 4,530 megawatts of net summer capacity across four reactors. The Grand Gulf station in Port Gibson, Mississippi, holds the largest single reactor at about 1,400 megawatts.

Most sites are small. Twenty-two plants operate a single reactor, 31 operate two, three operate three and one operates four. Another 19 retired reactors at 15 sites sit in various stages of decommissioning.

Fleet capacity has held steady even though the reactor count has fallen since 2012, because uprates at individual plants added megawatts to units already in service. EIA projects in its Annual Energy Outlook 2026 baseline case that total nuclear capacity stays relatively stable through 2050, while the nuclear share of national generation slips from 17 percent in 2025 to between 12 and 15 percent by 2050.

The oldest unit still running, Nine Mile Point Unit 1 in New York, entered commercial service in December 1969. The newest, Vogtle Unit 4 in Georgia, began commercial operation in April 2024.

Source: U.S. Energy Information Administration - https://www.eia.gov/energyexplained/nuclear/us-nuclear-industry.php