US nuclear plants ran at a 93.0 percent capacity factor in 2023, one of the two highest figures recorded in the industry's history and a level no other generating source in the country matches. The number comes from Nuclear Energy Institute statistics compiled from Energy Information Administration reporting, which tracks annual nuclear output from 1971 forward.

That performance translated into 775.4 million megawatt hours of nuclear generation in 2023, or 18.2 percent of all electricity produced in the United States. The fleet delivered that share from 95,773 MW of net summer capacity, a smaller installed base than the 101,419 MW the industry carried in 2011.

The long arc of the data shows output gains driven by operating performance. In 1971 US reactors produced 38.1 million megawatt hours, 2.4 percent of national generation, at a capacity factor of 48.2 percent. Capacity factor crossed 85 percent in 1999, reached 90.3 percent by 2002, and has stayed above 86 percent every year since, peaking at 93.4 percent in 2019.

Nuclear's share of the national mix has held between 18 and 20 percent for more than three decades, even as total US electricity generation climbed from about 3.04 billion megawatt hours in 1990 to about 4.23 billion in 2022. The fleet held that share while shrinking. Kewaunee, Vermont Yankee, Fort Calhoun, Oyster Creek, Pilgrim, Three Mile Island Unit 1, Indian Point 2 and 3, Duane Arnold and Palisades all left the fleet between 2013 and 2022, trimming net summer capacity by several thousand megawatts across the decade.

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