U.S. nuclear plants ran at roughly 91 percent capacity factor in 2025, the highest utilization of any generating technology on the American grid.

Capacity factor measures actual output against what a plant could produce running flat out for the full year. The U.S. nuclear fleet averaged about 92.3 percent in 2024 and has held in a narrow band near 90 percent for more than a decade, a level no other dispatchable or intermittent source matches. The global nuclear fleet averaged 83 percent in 2024, placing American operators roughly eight points above the international benchmark.

The stability comes from operating practice rather than new construction. The 94 reactors in commercial service in the United States are refueled on 18 to 24 month cycles, with outage durations compressed through pre staged parts and planning that treats every idle day as lost generation. Unplanned outage rates have fallen to a fraction of what the fleet recorded in the 1980s, when capacity factors sat in the 60 percent range.

Nuclear supplied about 18 percent of U.S. utility scale electricity generation in 2025 out of roughly 4,429 billion kilowatthours in total net generation. The share has hovered near 20 percent since 1990 even as total generation grew, because a fleet of comparable size kept producing more from the same reactors.

Uprates now underway across multiple operators are designed to extend that pattern, adding megawatts at licensed sites without a new construction schedule.

Source: ANS Nuclear Newswire - https://www.ans.org/news/article-6967/us-nuclear-capacity-factors-stability-and-energy-dominance/