The United States operated 96 commercial nuclear reactors at 57 plants across 28 states as of early 2026, according to Energy Information Administration data, with combined net summer generating capacity near 98,441 megawatts.

The fleet posted an average annual capacity factor of 91% in 2025, the highest figure among all US generation sources. Capacity factor measures actual output against theoretical maximum output over the same period, so a 91% reading indicates the fleet ran at or near full power for the large majority of hours in the year.

Nuclear generation accounted for roughly 19% of total US electricity in the most recent full year of data. That share has held remarkably steady even as the reactor count declined from its 2012 peak.

The explanation is uprates. Power uprate modifications at individual plants increased licensed output at existing units, offsetting retirements and allowing the fleet to maintain both absolute generation and its share of the national mix with fewer reactors operating.

Fuel cycle characteristics contribute to the high capacity factor. Reactors refuel on 18 to 24 month cycles, taking the unit offline for several weeks, and operators schedule those outages during shoulder seasons when system demand is lower. Between refueling outages, units run continuously at rated power.

EIA maintains detailed nuclear and uranium datasets covering generation, capacity, fuel purchases and spent fuel storage, updated monthly and annually. Those series form the reference baseline against which proposed capacity additions and license renewals are measured.

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