Data centers make heat all year long – here’s how the ground can hold onto it until winter

Epic Systems in Verona, Wisconsin, has drilled about 6,100 wells, 300 to 800 feet deep, to heat and cool roughly 40 campus buildings using waste heat from its 3.5-megawatt data center. Unlike ordinary ground-source heat pumps, the system pushes heat into the rock each summer and recovers it months later each winter, using the ground itself as storage rather than any tank or battery.

The Department of Energy reports Epic's buildings use about 25% less energy than comparable buildings in the same climate, though the company hasn't published what the system cost. A similar aquifer-based approach has supplied 60% to 80% of winter heat for a mixed-use complex in Bonn, Germany, since 2009.

The approach faces real limits: the heat only works for facilities built close by, and Epic's data center is small next to the 100-to-1,000-megawatt AI campuses now going up elsewhere. More than 141,000 documented orphaned oil and gas wells sit unplugged in the U.S. as a possible head start, but most states have no regulatory category for repurposing a well as heat storage rather than retiring it.

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