Microsoft deal propels Three Mile Island restart, with key permits still needed

Key regulatory permits for the plant’s new life, however, haven’t been filed, regulators say.

Big tech has led to a sudden surge in U.S. electricity demand for data centers needed to expand technologies like artificial intelligence and cloud computing. Nuclear energy, which is nearly carbon-free and broadly considered more reliable than energy sources like solar and wind, has become a popular option for technology companies with uninterrupted power needs and climate pledges.

“Nuclear plants are the only energy sources that can consistently deliver on that promise,” Constellation Chief Executive Officer Joe Dominguez said in a statement.

Constellation’s shares were up more than 20% by early afternoon to $251.42 and have risen more than 100% so far this year.

Power from the plant would be used to offset Microsoft’s data center electricity use, the companies said.

A relaunch of Three Mile Island, which had a separate unit suffer a partial-meltdown in 1979 in one of the biggest industrial accidents in the country’s history, still requires federal, state and local approvals.

Constellation has yet to file an application with federal nuclear regulators to restart the plant.

“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 said it expected the NRC review process to be completed in 2027.