The U.S. nuclear fleet remains one of the most reliable sources of electricity on the grid, according to figures from the Nuclear Energy Institute and the Energy Information Administration. As of early 2026, the country operated 96 commercial reactors at 57 plants across 28 states, with combined net summer capacity of 98,441 megawatts.

Reliability is the fleet's defining trait. The average annual capacity factor reached 91 percent in 2025, meaning plants produced electricity at 91 percent of their maximum possible output over the year. The fleet has posted a capacity factor of at least 90 percent every year since 2012, a level of consistency few other generation sources match.

That steady output translates into a large share of the nation's power. Nuclear plants supply almost 20 percent of U.S. electricity and roughly half of the country's carbon-free generation, running around the clock regardless of weather. The high capacity factor is why a relatively small number of reactors can produce such a substantial portion of national supply.

The data underscore why utilities and policymakers are working to keep existing reactors online and to restart idled units. As demand from data centers and electrification climbs, the reliability of the nuclear fleet has become a central consideration in grid planning across much of the country.

Source: NEI -- https://www.nei.org/resources/statistics/us-nuclear-generating-statistics