Nuclear power continues to play a vital role in U.S. electricity generation, contributing around 20% of the national supply. With 93 reactors operating across 28 states, the country maintains the world’s largest nuclear fleet.
Illinois tops the list, producing more than 8.8 million megawatt-hours (MWh) in January 2025 from its 11 reactors – more than any other state. Pennsylvania follows with nearly 7 million MWh, and South Carolina, Georgia, and Alabama round out the top five.
Georgia’s position is partly due to Vogtle Unit 3, which came online in mid-2023. It was the first new commercial U.S. reactor in more than 30 years.
“Georgia’s nuclear expansion shows long-term energy planning is still possible”
Nuclear reactors run nearly constantly, giving them a national average capacity factor of 92.7% – well above wind, solar, and fossil fuel sources. In states like South Carolina and Illinois, nuclear provides more than half the electricity used, and often generates surplus power that is exported to other states.
Old Nuclear Power Reactors, Extended Lives
Despite the lack of new construction in recent decades, many older reactors continue to operate thanks to license renewals. Nine Mile Point Unit 1 in New York, commissioned in 1969, remains the oldest functioning reactor in the country. Others, such as Florida’s Turkey Point Units 3 and 4 and Minnesota’s Monticello plant, are over 50 years old and still supplying power.
The U.S. Nuclear Regulatory Commission (NRC) has extended operating licenses from 40 to 60 years for many plants, and in some cases, to 80 years.
However, aging infrastructure brings concerns.
“The technical capability is there, but older facilities need significant upgrades to ensure continued safety”
A Patchwork of Nuclear Power Output
Arizona, though home to the largest single plant – Palo Verde – produces less nuclear energy overall than smaller states with more reactors. Virginia and Florida, with four and five reactors respectively, remain reliable producers.
The following table shows how the top states performed in January 2025:
| State | Reactors | Output (MWh) | Share of U.S. Total |
|---|---|---|---|
| Illinois | 11 | 8.83M | 12.3% |
| Pennsylvania | 9 | 6.96M | 9.7% |
| South Carolina | 7 | 4.89M | 6.8% |
| Georgia | 4 | 4.69M | 6.5% |
| Alabama | 5 | 4.16M | 5.8% |
Data from the U.S. Energy Information Administration shows these five states produced more than 40% of the nation’s total nuclear energy in a single month.
Eyes on the Future
While public concern and political resistance slowed new nuclear power development for decades, rising demand for stable, carbon-free energy is changing the conversation. The successful startup of Vogtle Unit 3 could signal a shift, though no new plants are expected to break ground soon.
New technologies, such as small modular reactors (SMRs), are in development, but commercial deployment remains years away.
“We’re watching a balancing act—keeping old plants running while evaluating new designs and funding models”
