<P> Nuclear power in the United States is provided by 99 commercial reactors with a net summer capacity of 100,350 megawatts (MW), 65 pressurized water reactors and 34 boiling water reactors . In 2016 they produced a total of 805.3 terawatt - hours of electricity, which accounted for 19.7% of the nation's total electric energy generation . In 2016, nuclear energy comprised nearly 60 percent of U.S. emission - free generation . </P> <P> As of September 2017, there are two new reactors under construction with a gross electrical capacity of 2,500 MW, while 34 reactors have been permanently shut down . The United States is the world's largest producer of commercial nuclear power, and in 2013 generated 33% of the world's nuclear electricity . </P> <P> As of October 2014, the NRC has granted license renewals providing a 20 - year extension to a total of 74 reactors . In early 2014, the NRC prepared to receive the first applications of license renewal beyond 60 years of reactor life, as early as 2017, a process which by law requires public involvement . Licenses for 22 reactors are due to expire before the end of the next decade if no renewals are granted . The Vermont Yankee Nuclear Power Plant was the most recent nuclear power plant to be decommissioned on December 29, 2014 . Another four aging reactors were permanently closed in 2013 before their licenses expired because of high maintenance and repair costs at a time when natural gas prices have fallen: San Onofre 2 and 3 in California, Crystal River 3 in Florida, and Kewaunee in Wisconsin, and New York State is seeking to close Indian Point in Buchanan, 30 miles from New York City . </P>

When was the last nuclear reactor built in the us