Are tech companies restarting Three Mile Island to power AI?
The claim: “Tech companies are restarting Three Mile Island to power AI.”
Partly. Constellation is restarting Three Mile Island Unit 1, renamed the Crane Clean Energy Center, under a 20-year agreement for Microsoft to buy its energy. Constellation says that helps match what Microsoft’s data centres in the PJM region use, not AI alone, and the power goes onto the grid. It isn’t the 1979 accident reactor: that was Unit 2, now being decommissioned. Unit 1 shut in 2019 for economic reasons. It isn’t running yet: Constellation expects 2027, and the regulator’s final decision is expected in 2027.
The bigger pictureOnce running, it would restore 835 megawatts to the grid, Constellation says. All the world’s data centres, of which AI is one part, used about 485 TWh of electricity in 2025.
Why the claim misleads
There is a real restart deal with Microsoft. But it’s for its data centres in general, it’s Unit 1 rather than the 1979 accident reactor, and it isn’t generating yet.
What nobody knows yet
- The price, and how much of Microsoft’s PJM data-centre use the plant covers, aren’t public.
- Whether 2027 holds: the regulator cleared the environmental review in September 2026, but its final restart decision is still to come.
- Hum couldn’t open the NRC’s own pages, so the regulator’s steps are as reported by the trade press.
Sources (8)
- Constellation Energy, press release (20 September 2024) Company says so
“Constellation (Nasdaq: CEG) announced today the signing of a 20-year power purchase agreement with Microsoft that will pave the way for the launch of the Crane Clean Energy Center (CCEC) and restart of Three Mile Island Unit 1”
Quote checked on the page, 25 Oct 2026 - Constellation Energy, press release (20 September 2024) Company says so
“Under the agreement, Microsoft will purchase energy from the renewed plant as part of its goal to help match the power its data centers in PJM use with carbon-free energy.”
Quote checked on the page, 25 Oct 2026 - Constellation Energy, press release (20 September 2024) Company says so
“The Unit 1 reactor is located adjacent to TMI Unit 2, which shut down in 1979 and is in the process of being decommissioned by its owner, Energy Solutions. TMI Unit 1 is a fully independent facility, and its long-term operation was not impacted by the Unit 2 accident.”
Quote checked on the page, 25 Oct 2026 - Constellation Energy, Crane Clean Energy Center page Company says so
“This new center, expected to go online in 2027, will: Restore 835 megawatts of reliable, clean, carbon-free energy to the grid”
Quote checked on the page, 25 Oct 2026 - American Nuclear Society, Nuclear Newswire (3 April 2026) News report
“The plant was originally shuttered in 2019 due to economic challenges in the energy market, with low natural gas prices outpacing nuclear and no state incentives for TMI’s carbon-free energy output.”
Quote checked on the page, 25 Oct 2026 - American Nuclear Society, Nuclear Newswire (9 June 2026), citing the NRC News report
“The final EA and FONSI are expected in September, according to the NRC’s Crane restart web page. A final decision on the restart is expected in 2027.”
Quote checked on the page, 25 Oct 2026 - World Nuclear News (28 September 2026) News report
“The US regulator, together with the Department of Energy Office of Energy Dominance Financing, has issued an environmental assessment and finding of no significant impact for environmental effects from proposed Federal actions related to reauthorising power operations at the Christopher Crane Clean Energy Center in Pennsylvania.”
Quote checked on the page, 25 Oct 2026 - IEA, Key Questions on Energy and AI (2026) Estimated
“electricity consumption from data centres roughly doubling from 485 TWh in 2025 to 950 TWh in 2030”
Quote checked on the page, 3 Oct 2026
Cite this
Constellation Energy, press release (20 September 2024), as quoted in Hum, “Are tech companies restarting Three Mile Island to power AI?”, https://humearth.org/q/nuclear-restarts (quote checked 25 Oct 2026).
Cite the original source first; Hum is where you found it.
What do Wh, kWh and TWh mean?
Wh is a watt-hour: a 1-watt light left on for an hour. 1 kWh = 1,000 Wh, and 1 TWh = 1 billion kWh. Hum compares each number with something everyday so you don’t need the units.
Send this answer
Three Mile Island: Unit 1 (not the 1979 accident reactor) is being restarted under a 20-year deal for Microsoft’s data centres. It isn’t running yet; Constellation expects 2027.