This spa’s water is heated by bitcoin mining

“I thought, ‘That’s interesting—we need heat,’” Goodman says of Bathhouse. Mining facilities typically use fans or water to cool their computers. And pools of water, of course, are a prominent feature of the spa.

It takes six miners, each roughly the size of an Xbox One console, to maintain a hot tub at 104 °F. At Bathhouse’s Williamsburg location, miners hum away quietly inside two large tanks, tucked in a storage closet among liquor bottles and teas. To keep them cool and quiet, the units are immersed directly in non-conductive oil, which absorbs the heat they give off and is pumped through tubes beneath Bathhouse’s hot tubs and hammams.

Mining boilers, which cool the computers by pumping in cold water that comes back out at 170 °F, are now also being used at the site. A thermal battery stores excess heat for future use.

Goodman says his spas aren’t saving energy by using bitcoin miners for heat, but they’re also not using any more than they would with conventional water heating. “I’m just inserting miners into that chain,” he says.

Goodman isn’t the only one to see the potential in heating with crypto. In Finland, Marathon Digital Holdings turned fleets of bitcoin miners into a district heating system to warm the homes of 80,000 residents. HeatCore, an integrated energy service provider, has used bitcoin mining to heat a commercial office building in China and to keep pools at a constant temperature for fish farming. This year it will begin a pilot project to heat seawater for desalination. On a smaller scale, bitcoin fans who also want some extra warmth can buy miners that double as space heaters.

Crypto enthusiasts like Goodman think much more of this is coming—especially under the Trump administration, which has announced plans to create a bitcoin reserve. This prospect alarms environmentalists.

The energy required for a single bitcoin transaction varies, but as of mid-March it was equivalent to the energy consumed by an average US household over 47.2 days, according to the Bitcoin Energy Consumption Index, run by the economist Alex de Vries.