Constellation Energy and Microsoft have inked a deal to power the restart of a unit at the Three Mile Island nuclear plant in Pennsylvania, marking the first-ever relaunch of its kind. However, regulatory approvals for the project have yet to be submitted, according to authorities.
Rising electricity demand driven by Big Tech, especially for data centres supporting AI and cloud computing, has increased interest in nuclear energy. Known for its near-zero carbon emissions and reliability compared to solar and wind, nuclear power has become a favored solution for tech companies with high energy demands and sustainability goals.
“Powering industries critical to our nation’s global economic and technological competitiveness, including data centres, requires an abundance of energy that is carbon-free and reliable every hour of every day, and nuclear plants are the only energy sources that can consistently deliver on that promise,” said Joe Dominguez, president and CEO, Constellation.
Following the announcement, Constellation’s shares surged over 20%, reaching $251.42, with the stock up more than 100% this year. Power from the plant is slated to help offset Microsoft’s data centre electricity use.
The relaunch of Three Mile Island—whose Unit 2 experienced a partial meltdown in 1979 in one of the nation’s most infamous industrial accidents—still awaits federal, state, and local approvals. Constellation has not yet submitted a formal application to federal nuclear regulators.
“It’s up to Constellation to lay out its rationale for justifying restart, so we’re prepared to engage with the company on next steps,” said Nuclear Regulatory Commission (NRC) spokesperson Scott Burnell.
Constellation anticipates completing the NRC review by 2027.
The project, expected to cost $1.6 billion, aims to revive the retired Unit 1 of the five-decade-old facility, with operations projected to begin by 2028. Unit 2 will remain closed.
Microsoft will purchase power from the revived plant under a 20-year agreement, with the unit supplying 835 megawatts of electricity, enough to power approximately 700,000 homes.
Though challenging, the restart has garnered support from tech companies as demand for clean energy rises. “This agreement is a major milestone in Microsoft’s efforts to help decarbonize the grid in support of our commitment to become carbon negative,” Bobby Hollis, vice president of energy at Microsoft, said.
“This is a valuable opportunity to invest in clean, carbon-free and affordable power — on the heels of the hottest year in Earth’s history. This will transform the local economy and presents a rare opportunity to power our economy with reliable clean energy that we can count on,” said Pennsylvania State Representative Tom Mehaffie (106th District).
Microsoft has also entered into a power purchase agreement with Washington-state fusion company Helion, aiming for a 2028 launch, despite skepticism about fusion’s commercial viability by that time.