Constellation Energy stock is starting 2025 in the same way it performed in 2024—way ahead of the pack.

Constellation Energy owns more nuclear power reactors than any other U.S. company.

Shares of the power plant owner jumped 8.4% on Thursday, second only to Vistra Energy among the S&P 500 companies. he S&P 500 index was down 0.2%.

Other nuclear energy stocks also jumped on Thursday. Centrus and Energy Fuels rose 11%; Vistra Energy rose 9%; Lightbridge rose 8%; Oklo rose 3%.

Constellation was soaring because it signed two deals with the U.S. government that are expected to pay out about $1 billion over the next several years. It’s a positive sign for the company, showing that it’s becoming a go-to player for any entity that needs a lot of electricity.

Constellation owns 21 nuclear reactors, more than any other U.S. company. Nuclear power has been in high demand from tech companies and others because it doesn’t emit carbon dioxide and it’s considered reliable. Constellation CEO Joe Dominguez said that historically “nuclear energy was excluded from many corporate and government sustainable energy procurements. Not anymore.”

Constellation has benefited over the past 18 months as tech companies race to sign electricity contracts to power their energy-hungry artificial intelligence data centers. The company even signed a deal with Microsoft to restart a mothballed nuclear reactor at Three Mile Island in Pennsylvania for data center power. Constellation stock rose 91% in 2024 after rising 36% in 2023.

The government deal announced Thursday comes in two parts. The first is a 10-year contract valued at $840 million to supply government operations with more than one million megawatt-hours (or one terawatt-hour) a year, beginning in 2025. Federal agencies use about 50 terawatt-hours a year in total.

A portion of the new power will come from investments that Constellation is making to increase the power output at its existing nuclear plants, known as “uprating” the plants. It can take more than a decade to build a new nuclear reactor, so uprating could be a significant and lucrative source of new nuclear power over the next few years.

The second part of the deal is a $172 million contract to upgrade five government buildings to make then more energy efficient by modernizing the heating and ventilation systems and other services. Those changes should take about three and a half years to complete.