Microsoft's 20-year PPA to restart Three Mile Island Unit 1 as the Crane Clean Energy Center is a nuclear bet on AI power demand

In September 2024, Constellation Energy announced it would restart the shuttered Three Mile Island Unit 1 reactor in Pennsylvania — rebranded the Crane Clean Energy Center (CCEC) — under a 20-year power purchase agreement with Microsoft. Per Constellation, "The CCEC is expected to be online in 2028" and will "add approximately 835 megawatts of carbon-free energy to the grid." The plant is a conventional light-water reactor being returned to service, not new construction.

The deal is one of the clearest physical signatures of the inference-dominant AI compute era: because inference runs continuously — every deployed model serving requests 24 hours a day — hyperscaler compute translates into sustained, baseload electricity demand rather than episodic spikes. Restarting a firm, carbon-free 835 MW generator is a way to buy that baseload directly rather than competing for it on the open grid.

Three Mile Island is a freighted site — Unit 2 was the location of the 1979 partial meltdown, the worst commercial nuclear accident in US history. Unit 1, a physically separate reactor, operated safely until it was retired for economic reasons in 2019; it is Unit 1 that is being restarted.

This is the light-water, restart-a-legacy-plant path. Google's parallel bet takes a technologically distinct route with a non-light-water molten-salt reactor. Whether either project's timeline survives contact with the grid is the open question raised by the US interconnection-queue backlog.