The US nuclear fleet operated at a capacity factor above 92 percent in 2024, the highest of any generating source in the country. Capacity factor measures actual output against the maximum a plant could produce running continuously, which makes it the cleanest single comparison of reliability across generation types.

Total output reached more than 782.0 billion kilowatt hours according to Energy Information Administration Electric Power Monthly reporting, the largest nuclear generation total of any country. Through the first 11 months of 2025, net generation increased 1.0 percent against the same period in 2024.

That increase came without new reactors entering service during the period. It reflects uprates, shorter refueling outages, and improved plant availability across the existing fleet, which is the only lever operators hold when adding capacity takes a decade.

Nuclear is projected to supply roughly 18 percent of US electricity generation during 2026, holding the same share it carried in 2025. Because total generation is rising, a flat percentage share means absolute nuclear output must also rise to keep pace.

The Nuclear Energy Institute maintains the long running capacity factor series covering 1980 through 2021 and generating statistics from 1971 forward. EIA publishes the current monthly data, with recent releases dated June 2026.

Source: Nuclear Energy Institute - https://www.nei.org/resources/statistics/us-nuclear-generating-statistics