Microsoft and Constellation Energy announced a new power purchase agreement enabling the restart of the Three Mile Island Unit 1 nuclear reactor in Pennsylvania, adding approximately 835 MW of carbon-free energy to the 13-state PJM grid.

Under the new 20-year agreement, Microsoft will purchase energy from the renewed plant to help match the power its data centers in PJM with carbon-free energy.

The agreement comes as Microsoft, along with its tech giant peers, look to address the growing emissions impact of their rapidly expanding data center footprints. While Microsoft has set 2030 goals to become carbon negative and to reduce Scope 3 emissions by more than half compared to 2020, the company recently reported that Scope 3 emissions in 2023 were actually more than 30% higher than in 2020, driven largely by significant growth in data centers to meet increasing demand for AI computing power. Microsoft has also put in place a “100/100/0 clean energy goal,” with the company targeting having 100% of its electricity consumption, 100% percent of the time, matched by purchases from zero carbon energy sources by 2030.

Microsoft said earlier this year that it was launching a company-wide initiative to identify and develop measures to address its Scope 3 emissions challenges.

Bobby Hollis, VP of Energy, Microsoft, said:

“This agreement is a major milestone in Microsoft’s efforts to help decarbonize the grid in support of our commitment to become carbon negative. Microsoft continues to collaborate with energy providers to develop carbon-free energy sources to help meet the grids’ capacity and reliability needs.”

The deal marks Constellation’s largest-ever power purchase agreement, and will require significant investments to restore the Unit 1 reactor, which was shut down in 2019 for economic reasons, including the turbine, generator, main power transformer and cooling and control systems. The Unit 1 reactor is located adjacent to the Unit 2 reactor, which was shut down after an infamous accident in 1979. Constellation said that the restart will require regulatory approvals and a comprehensive safety and environmental review, and that the company will pursue license renewal that will extend plant operations to at least 2054.

The plant, to be named the Crane Clean Energy Center (CCEC) after former Constellation CEO Chris Crane, is expected to be online in 2028.

Constellation President and CEO Joe Dominguez said:

“Powering industries critical to our nation’s global economic and technological competitiveness, including data centers, 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. Before it was prematurely shuttered due to poor economics, this plant was among the safest and most reliable nuclear plants on the grid, and we look forward to bringing it back with a new name and a renewed mission to serve as an economic engine for Pennsylvania.