The U.S. nuclear fleet continues to deliver steady, high-output performance, according to figures compiled by the Nuclear Energy Institute. The country's licensed commercial reactors generate close to 20 percent of national electricity, a share that has held remarkably stable even as the overall power mix shifts.

Reliability is the fleet's defining trait. The average annual capacity factor for U.S. nuclear plants reached 91 percent in 2025, meaning the reactors produced electricity at nearly their full rated output across the year. That figure outpaces every other major generation source. Coal, gas, wind, and solar all operate at lower capacity factors because of fuel cycles, maintenance, market dispatch, or the intermittency of weather-dependent resources.

The scale behind those percentages is substantial. The operating reactor fleet represents tens of gigawatts of net summer capacity running around the clock, providing the kind of firm baseload power that grid operators rely on to balance variable resources. Because reactors run continuously between refueling outages, they anchor system reliability in a way few other sources match.

The performance data carries added weight as electricity demand climbs from data centers, electrification, and manufacturing. A fleet that already runs near maximum output has limited headroom to absorb new load without added capacity, which helps explain the policy focus on uprates, license renewals, and new reactor designs. The consistency of nuclear generation makes it a central element of plans to meet rising baseload demand.

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