Microsoft rents Three Mile Island to power data centers

Constellation Energy signed its largest-ever power purchase agreement on Friday to allow tech giant Microsoft to use the energy produced by a now decommissioned unit on Three Mile Island, according to a company statement. Under the 20-year agreement, Microsoft will purchase energy produced by one of the two nuclear units on the island. TMI Unit 1 will stay online for decades under the agreement and is expected to add over 800 megawatts of carbon-free energy to the grid, deliver $3.6 billion in state and federal tax revenue, add $16 billion to Pennsylvania’s GDP, and reduce 61 million tons of CO2 emissions across 20 years, Constellation said.

Is restarting Three Mile Island safe? The nuclear site became infamous after TMI Unit 2 had a partial nuclear meltdown in 1979. TMI Unit 1 is a fully independent facility, and its long-term operation was not impacted by the Unit 2 accident, Constellation said in its release. Constellation purchased TMI Unit 1 in 1999, then retired it for economic reasons about a decade later. The plant had the ability to generate enough energy to power over 800,000 average homes, Constellation said.

The energy company must restore the plant’s turbine, generator, and main power transformer, along with cooling and control systems. The U.S. Nuclear Regulatory Commission, along with other state and local agencies, must also perform reviews and approve permits for the unit’s reactor to restart. Constellation expects TMI Unit 1 to be back online by 2028.

What does Microsoft want to do with that much energy? Microsoft plans to power its data centers with carbon-free energy, Constellation said. The agreement is a milestone for Microsoft’s commitment to being carbon-negative, Microsoft’s Vice President of Energy Bobby Hollis said. Tech analysts believe the nuclear deal will power Microsoft artificial intelligence data centers. It is well known that the data centers that train artificial intelligence language models use inordinate amounts of energy.