U.S. nuclear power plants now run far more consistently than they did when the industry was young, according to generating statistics compiled by the Nuclear Energy Institute using data from the U.S. Energy Information Administration. In 1980, the average capacity factor across the U.S. nuclear fleet was 56.3 percent, meaning reactors produced only about half of the electricity they were technically capable of generating over the course of a year. By 2023, that figure had climbed to 93.0 percent.

The gain reflects decades of operational and engineering improvements rather than a large increase in the number of reactors. The U.S. fleet has actually shrunk from its peak, as several older plants retired over the past two decades. Utilities responded by running the remaining reactors closer to their full rated capacity, cutting the length and frequency of both planned and unplanned outages.

Nuclear power supplied 18.2 percent of total U.S. electricity generation in 2023, drawing on a fleet with a combined summer capacity of about 95,773 megawatts, according to NEI's tracking of EIA data. That combination of a high capacity factor and a large base of installed capacity is why nuclear plants continue to supply a share of the grid disproportionate to their reactor count compared with intermittent generation sources.

Grid operators and utility planners point to capacity factor as one of the clearest measures of how much a power source can be relied upon for baseload demand, a factor increasingly relevant as data centers and manufacturing facilities across the country seek firm, round the clock electricity supply.

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