The US nuclear fleet remains one of the most reliable sources of electricity on the grid, operating at a 92 percent capacity factor in 2024, according to Nuclear Energy Institute statistics. That figure means the reactors ran near their maximum output for the large majority of the year, a level of reliability few other generation sources match.

The scale of the contribution is significant. Electric utilities in the United States operate 94 nuclear reactors, which together supplied about 19 percent of national electricity generation in 2024. Nuclear has held roughly a fifth of the US power mix for years, providing steady output regardless of weather or time of day.

The capacity factor has stayed consistently high. In 2023, the fleet averaged 90.3 percent while supplying about 19.1 percent of US electricity, underscoring how stable nuclear performance has been across recent years. Maintaining that level requires disciplined refueling schedules and maintenance planning, since each reactor spends only limited time offline.

Those numbers matter as demand climbs. With electricity consumption rising and data centers seeking firm, around-the-clock power, the existing nuclear fleet's high capacity factor makes it a valuable baseload resource. License renewals and reactor restarts aim to keep that capacity on the grid longer while new construction adds to it.

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