Constellation Energy plans to reopen Three Mile Island Unit 1 under a power purchase agreement with Microsoft to sell about 835 MW to serve the company’s data centers.

Constellation announced the reopening in a press release Sept. 20, exactly five years after it took the nuclear generator offline for economic reasons. In its new life, the generator has been renamed the Crane Clean Energy Center (CCEC) in memory of Exelon CEO Chris Crane, who died in April 2024. (See Exelon to Close Three Mile Island.)

“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,” Constellation CEO Joe Dominguez said in the announcement. “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.”

Constellation aims to bring the unit back online in 2028 and will seek a license renewal from the Nuclear Regulatory Commission to continue operating the generator through at least 2054. Restarting the unit will require a $1.6 billion investment, including upgrades to the turbine, generator and transformer. Safety and environmental reviews will be required from the NRC, as well as local and state permits. The adjacent TMI Unit 2, which partially melted down in 1979, is owned by Energy Solutions and is in the process of being decommissioned.

While the generator will interconnect with PJM, the power will be supplied directly to Microsoft, and no energy nor capacity will be offered in the RTO’s markets.

Microsoft Vice President of Energy Bobby Hollis said the carbon-free energy provided by CCEC will help the company meet its clean energy targets. The PPA will be effective for 20 years.

“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 grid’s capacity and reliability needs,” he said.

Data center load has been a significant driver of rapidly increasing load forecasts in PJM and has been highlighted as one factor behind a spike in capacity prices in the 2025/26 capacity auction. (See “PJM Discusses 2025/26 Auction Results,” PJM MRC/MC Briefs: Aug. 21, 2024.)

The RTO’s 2024 load forecast, which is based on historic economic trends, includes large load additions in the AEP, APS, Dominion and PS zones, reflecting changes in consumption that utilities identified. Dominion estimated 2,666 MW of additional load in 2025, which it estimates will balloon to 21,563 MW in 2039. American Electric Power estimates 1,738 MW in 2025, growing to 3,624 MW in 2039.

Data centers have sought to co-locate with nuclear power plants, which would pull capacity out of PJM’s market over the objections of utilities and state regulators. Talen Energy and Amazon Web Services reached an agreement earlier this year to sell a data center Talen built adjacent to its Susquehanna Nuclear Plant and supply it with behind-the-meter energy.

PJM has asked FERC to approve an amendment to the generator’s interconnection service agreement to reduce the maximum output, and capacity, the generator offers into PJM. Exelon and AEP filed a joint protest arguing that co-located load benefits from the wider transmission grid and should be subject to relevant fees. They also argued there are unresolved questions about how a novel configuration could affect the grid. The Pennsylvania Public Utility Commission filed in support of the utilities’ protest (ER24-2172). (See Talen Energy Deal with Data Center Leads to Cost Shifting Debate at FERC.)

Pennsylvania Politicians, Nuclear Experts Support Reopening

Pennsylvania Gov. Josh Shapiro (D) gave the reopening his support in a statement provided through Constellation’s announcement, saying the state’s nuclear industry provides “safe, reliable, carbon-free electricity.”

“Under the careful watch of state and federal authorities, the Crane Clean Energy Center will safely utilize existing infrastructure to sustain and expand nuclear power in the commonwealth while creating thousands of energy jobs and strengthening Pennsylvania’s legacy as a national energy leader.”

That support was echoed by state Rep. Tom Mehaffie (R), U.S. Rep. Scott Perry (R) and Bart Shellenhamer, chair of the Board of Supervisors for Londonderry Township, where the CCEC is located.

“This unit was a good neighbor to Londonderry Township and our surrounding region for 45 years, with a workforce dedicated to contributing to area nonprofits and supporting the local economy,” Shellenhamer said. “The Crane Clean Energy Center will bring billions in new infrastructure investment and help support area businesses, schools and public services that improve quality of life for the whole region.”

Michael Goff, acting assistant secretary of the U.S. Department of Energy’s Office of Nuclear Energy, said the reopening is a milestone for Pennsylvania and the country. “Always-on, carbon-free nuclear energy plays an important role in the fight against climate change and meeting the country’s growing energy demands,” he said.

Constellation purchased TMI 1 in 1999 and operated the unit through 2019, when it opted to deactivate the generator rather than buy more fuel. The company asked the Pennsylvania General Assembly to pass subsidies for the plant’s continued operation years ahead of the retirement. While both chambers had bills on their dockets, their prospects were unclear. (See Pa. Lawmaker Contends TMI Rescue Unlikely.)