Microsoft brings back the Three Mile Island nuclear plant
2024-09-20 · Publisher : Microsoft · Domain : Artificial Intelligence
Constellation Energy signs a 20-year power purchase agreement with Microsoft to restart Three Mile Island Unit 1, shut down in 2019. Energy becomes a direct stake in the AI race.
What changes
- A 20-year power purchase agreement: Microsoft will buy the reactor's output for its data centers.
- About 835 MW of carbon-free electricity, with a restart targeted for 2028.
- Constellation plans 1.6 billion USD to restart Unit 1, shut down in 2019 for economic reasons.
- The site is renamed Crane Clean Energy Center; Unit 1 is independent of Unit 2, damaged in 1979.
- Constellation describes the deal as the largest power purchase agreement in its history.
On September 20, 2024, Constellation Energy announced a 20-year power purchase agreement with Microsoft that would allow Unit 1 of the Three Mile Island plant in Pennsylvania to restart. The site, known for the 1979 accident at Unit 2, became a symbol of AI's energy needs. ### What happened - Microsoft committed to buying, for 20 years, the electricity produced by Unit 1, shut down in 2019 for economic reasons but never dismantled. - Constellation planned to invest 1.6 billion USD in the restart, subject to approval by the U.S. Nuclear Regulatory Commission (NRC). - The plant was renamed the Crane Clean Energy Center. - Constellation stressed that Unit 1 is fully independent of Unit 2, which is being decommissioned. ### Key figures | Item | Value | |---|---| | Contract length | 20 years | | Capacity | about 835 MW | | Restart target at announcement | 2028 | | Announced investment | 1.6 billion USD | | Direct and indirect jobs (Constellation estimate) | 3,400 | ### Why it is a turning point Training and running AI models drive up data center power consumption. Rather than buying electricity from the grid, a cloud giant directly funds the reopening of a nuclear reactor. In the following months, Google, Amazon and Meta in turn announced nuclear deals, including small modular reactors. ### Caveats The restart depends on regulatory approvals and grid connection. In November 2025, the U.S. Department of Energy granted the project a 1 billion USD loan, and Constellation now mentions a restart as early as 2027. The contract covers only a fraction of Microsoft's total needs. ### Key takeaways Generative AI is no longer just about chips: access to abundant, carbon-free electricity becomes a competitive factor, pushing digital players to invest in energy production.
Links
- Constellation Energy — Constellation to Launch Crane Clean Energy Center
- CNBC — Constellation Energy to restart Three Mile Island and sell the power to Microsoft
- Utility Dive — Constellation plans 2028 restart of Three Mile Island unit 1, spurred by Microsoft PPA
- The Register — US pumps $1B into Three Mile Island nuclear plant reboot (novembre 2025)
Tags : IA, Énergie, Nucléaire, Centres de données, Microsoft