US nuclear power plants ran at an average annual capacity factor of 91% in 2025, higher than any other type of power plant, according to generating statistics. The figure measures how much electricity a plant produced relative to its maximum possible output, and nuclear's high reading reflects its role as a steady baseload source.

The fleet's scale remains substantial. The country's operating reactors carry a combined net summer generating capacity of about 98,441 megawatts. Together they supply almost 20% of total US electricity, a share the fleet has held consistently even as overall demand has grown.

The reliability gap between nuclear and other sources is significant. While nuclear plants operated near 91% of capacity, most other generation types run at considerably lower factors because of fuel, weather, or demand variability. That consistency makes nuclear output valuable for grid operators managing round-the-clock load.

The statistics underscore why utilities and policymakers are working to preserve the existing fleet through license renewals and restarts. High capacity factors mean each reactor delivers a large, predictable volume of carbon-free electricity, a profile increasingly sought after as data centers and electrification push up demand for firm, always-available power across the grid.

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