The United States operated 96 commercial nuclear reactors at 57 power plants across 28 states as of March 2026, with combined net summer electricity generating capacity of 98,441 megawatts. The Nuclear Energy Institute publishes the fleet statistics alongside historical generation and capacity factor series.

The average annual capacity factor for US nuclear plants reached 91 percent in 2025. Capacity factor measures actual output against theoretical maximum output across a full year, and a 91 percent figure means the fleet ran at nearly full rated power for all but roughly one month of combined refueling and maintenance downtime.

That performance level distinguishes nuclear from other generation sources on a utilization basis. A 98,441 megawatt fleet operating at 91 percent produces substantially more annual energy than a nominally larger fleet of intermittent capacity operating at a lower factor, which is why nameplate capacity comparisons across generation types can mislead.

Nuclear electricity accounted for 19 percent of total US electricity generation in 2024. Federal projections place the share at 18 percent for 2026, effectively flat against 2025.

The institute maintains generating statistics extending back to 1977, covering megawatts generated, capacity factor, nuclear fuel share and total electricity generation, which allows direct comparison of current fleet performance against the operating record of prior decades.

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