Nuclear Fleet Operator / Power Generator
Baltimore-based power company and the largest operator of nuclear plants in the United States. Spun out of Exelon in 2022. Restarting Three Mile Island Unit 1 for Microsoft under a 20-year PPA. Closed the $26.6B acquisition of Calpine in January 2026, adding the largest fleet of natural gas plants in the U.S.
Three Mile Island Restart
Constellation is investing approximately $1.6 billion to restart Three Mile Island Unit 1, the 835 MW pressurized water reactor in Middletown, Pennsylvania that shut down in 2019 due to market conditions. The restart is backed by a $1 billion federal loan guarantee from the Department of Energy and a 20-year power purchase agreement with Microsoft.
The project, officially named the Crane Clean Energy Center, was originally targeted for restart by mid-2028. As of early 2026, Constellation has indicated the project is ahead of schedule, with a potential restart as early as 2027. Federal regulators held public hearings on the restart plans in February 2026.
Calpine Acquisition
Constellation announced the acquisition of Calpine on January 10, 2025, and closed the deal on January 7, 2026. The transaction had an equity purchase price of approximately $16.4 billion, comprising $4.5 billion in cash and 50 million shares of Constellation stock. Including assumed debt, the total enterprise value was approximately $26.6 billion.
Calpine operates the largest fleet of natural gas-fired combined cycle plants in the United States. The acquisition positions Constellation as both the dominant U.S. nuclear operator and a major gas generator, giving it a diversified dispatchable fleet that can serve industrial and data center customers seeking around-the-clock carbon-free and low-carbon power.
Nuclear Fleet
Constellation operates 21 reactors — the largest US nuclear fleet. Total capacity exceeds 32 GW across nuclear, wind, solar, hydro, and gas. In January 2026, Constellation signed a 1.1 GW deal with Meta from the Clinton Power Station in Illinois. Plans: +1.5 GW via restarts and uprates by 2035; 9+ GW from license renewals over the same period.
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