Electricity generation from U.S. nuclear power plants totaled 807.1 million megawatthours (MWh) in 2018, slightly more than the previous peak of 807.0 million MWh in 2010, based on preliminary annual data. Although several nuclear power plants have closed since 2010, a combination of added capacity through uprates and shorter refueling and maintenance cycles allowed the remaining nuclear power plants to produce more electricity. In the near future, however, EIA expects that U.S. nuclear power output will decline.
Between 2010 and 2018, only one new nuclear power plant came online in the United States. The Tennessee Valley Authority's (TVA) Watts Bar Unit 2 nuclear power reactor came online in the fall of 2016, providing 1.2 gigawatts (GW) of additional power. Seven plants with a combined capacity of 5.3 GW had retired since 2013. As of the beginning of 2019, the United States had 98 nuclear power reactors at 60 plants, but two plants—Pilgrim, Massachusetts’s only nuclear plant, and Three Mile Island in Pennsylvania—are expected to retire later this year, based on announced retirements.
Despite changes in capacity from plants coming online or retiring, the U.S. nuclear power fleet maintained electricity generation near 800 million MWh for over a decade for several reasons. Several plants commissioned uprates, which involves modifying the plant to increase its generating capacity. EIA recorded 2.0 GW of thermal power uprates between 2010 and 2018, nearly the equivalent of adding two new reactors similar to Watts Bar Unit 2.
Nuclear power plants have also shortened the time they are out of operation for refueling or maintenance. Nearly all of the recent reduction in outage duration is attributed to shorter outages for refueling operations. In 2018, the average nuclear reactor outage was about 25 days. Nuclear power plants typically refuel every 18 to 24 months, so some of the annual fluctuations in nuclear output are largely attributable to how maintenance cycles align across the fleet.
The combination of uprates, shorter outage durations, and balance-of-plant thermal efficiency improvements led the U.S. nuclear power fleet in 2018 to see its highest capacity factor on record, at 92.6%.
The 2018 peak level of U.S. nuclear generation is not likely to be surpassed in the coming decades. Based on project information reported to EIA, only two new nuclear reactors are scheduled to come online in the near future. Georgia's Vogtle Units 3 and 4, which are planning to come online in 2021 and 2022, respectively, would provide 2.2 GW of additional power. However, this new capacity will not offset the capacity that is expected to retire in the next seven years, based on announced retirements. Two plants will retire later this year, three more in 2020, and four more in 2021. By 2025, U.S. nuclear capacity will fall by 10.5 GW from the closings of twelve reactors.
Opportunities for further uprates, which had offset the loss of nuclear electricity capacity in recent years, are shrinking. According to the NRC, only 60 megawatts (MW) of thermal uprate applications are anticipated through 2020. Current market conditions—the combination of relatively low wholesale electricity prices and flat demand growth—do not provide the financial incentives plant owners require to invest in improvements that would increase output from the existing fleet.
As more nuclear plants close, EIA projects that net electricity generation from U.S. nuclear power reactors will fall by 17% by 2025 in the Annual Energy Outlook 2019 Reference case. The loss of electricity production from nuclear power is expected to be largely offset by output from new natural gas, wind, and solar power plants.
