Three Mile Island Could Power Microsoft’s AI Projects

Microsoft recently signed a 20-year agreement to buy nuclear energy that will lead to the restart of Three Mile Island Unit 1 near Harrisburg. The company will use the carbon-free power to match the demand from its expanding data centers in the Mid-Atlantic region.

Three Mile Island was the site of a 1979 partial nuclear meltdown at Unit 2, which is now being decommissioned. However, the adjacent Unit 1 was undamaged and is fully independent. It operated until 2019, when its became too costly compared to other sources of energy generation, such as natural gas-fueled power plants.

But as demand for a steady supply of carbon-free power increases from companies that are rapidly expanding data centers and developing artificial intelligence, the economics have changed. Constellation, which purchased TMI Unit 1 in 1979, said that before the expected restart in 2028, it would invest in upgrades to the plant, including the turbine, generator, main power transformer, and cooling system. It must also seek approval from the U.S. Nuclear Regulatory Commission, as well as permits from state and local agencies.

Prior to its shutdown, TMI Unit 1 was capable of producing 837 megawatts of energy, enough to power 800,000 homes. That additional power will be added to the Mid-Atlantic electric grid operated by PJM, which includes 13 Mid-Atlantic states (including Pennsylvania) and the District of Columbia.

PJM has been sounding warnings about the need for more energy generation in the Mid-Atlantic, as a continued rise in demand is expected in the coming decade. The North American Reliability Corp., an international regulatory authority that oversees grid reliability, also warned in its 2023 Long-Term Reliability Assessment that a large increase in electricity demand is forecast to occur. This trend is being driven by the rise of electric vehicles, electrification of industrial processes, and the surge of energy-hungry data centers coming online.

Data centers are large warehouse-type facilities that house computer and cloud infrastructure for running applications and delivering and storing information. They are one of the most energy-intensive building types, using 10–40 times more energy per square foot than the typical office building and now accounting for almost 2% of the electricity use in the United States, according to the EIA. That percentage is expected to rapidly increase.

Secretary of Energy Jennifer Granholm recently suggested at an AI energy summit that artificial intelligence companies should supply their own clean energy for their data center projects.

TMI Unit 1 will be renamed the Crane Clean Energy Center, and is expected to create 3,400 direct and indirect jobs and add $16 billion to the state’s gross domestic product.

The PPA is the second this year in which a data center owner has signed an agreement to buy nuclear power. In March, Amazon Web Services agreed to purchase 960 MW of electric capacity from the Talen Energy Susquehanna plant, which is also in central Pennsylvania.