Bathhouse is a super-trendy spa located in Williamsburg, Brooklyn, with a new location set to open sometime in the near future in Manhattan’s Flatiron district. If its sans serif font and ultra-minimalist website don’t already scream New York City Elite, then the way it heats its pools absolutely shouts it from the rooftops: Bathhouse mines bitcoin to warm its baths.
In the endless battle whereby bitcoin supporters and crypto bros try desperately to prove that mining bitcoin isn’t demonstrably terrible for the environment, I didn’t expect a bougie spa to enter the chat, but here we are. Though Bathhouse first revealed it was heating its pools via bitcoin mining earlier in 2023 with an Instagram post, an October 24 X post from investigative journalist Paris Martineau has kicked up the conversation again, as she shared a picture of the Flatiron storefront alongside screenshots from Bathhouse’s website about its bitcoin baths.
“We started mining Bitcoin in 2022 as a pilot project to test out on a small scale, heating a couple of pools. This solution would be scalable to anybody needing hot water, whether that was for heating pools, domestic hot water or building heating applications such as radiant flooring,” a response on Bathhouse’s FAQ page reads. “We purchase off-the-shelf ASICs [application-specific integrated circuits], which are computers designed specifically for Bitcoin mining. We remove the fans and convert them for immersion cooling because they typically come designed to run air-cooled. Then, the ASICs are immersed in a tank filled with dielectric fluid [a liquid electrical insulator] with a pump and a heat exchanger on the tank.”
The FAQ goes on to assert that, because they’re using the heat from the miners to heat their pools rather than an electric heater, Bathhouse is “essentially energy-neutral.” This immediately set off alarm bells—granted, I know very little about electrical engineering, but there are mountains of proof that bitcoin mining is a massive energy suck, so it’s hard to believe Bathhouse is using less energy than if it was heating its pools with traditional electrical heaters.
So, I reached out to Linus of Linus Tech Tips, who has an at-home setup similar to Bathhouse’s, whereby his gaming PCs heat his pool and his pool cools his gaming PCs, to ask about the efficiency of such a rig.
“The larger the body of water and the higher the target temperature, the more ASICs or servers or other sorts of systems you might need in order to heat it,” he explained over email. “The calculation is fairly straightforward though. Nearly 100% of the energy from a computer or a mining device is converted to waste heat. That means depending on the efficiency of your heat capture (if you can pull from both the processors and power supplies somehow, for example), you could conceivably dump nearly all of the energy spent into a pool or hot tub.”
“You would never expect to achieve perfect balance between the heat output of your systems and the energy needs of your water and you would basically always have to top up with conventional gas fired or electric heating,” he pointed out. When I asked if Bathhouse’s energy-neutral claims had any veracity, he said that was a “complicated question.” He continued:
It can certainly be LESS wasteful than dumping waste heat into the surrounding environment where it may need to be carried away somehow (like when we run our gaming systems in our bedroom, then turn on our air conditioning to remove the heat). But there are ways to heat a body of water that are MUCH more efficient than resistive heating where watts of power consumed = watts of effective heating. According to energy.gov, using a heat pump rather than a mining ASIC could cut electricity usage by 50%. That heat pump wouldn’t be doing any useful WORK at the same time, but some would argue neither are those ASIC miners, so I’ll leave that question to the philosophers. Also, all of that ignores the energy losses associated with carrying the heat from wherever the mining/server machines are to the pool. No insulation is perfect.
I’m no expert, but that doesn’t sound energy neutral to me.
I’ve been to Bathhouse once in 2021, as part of a birthday gift for my fiance. I shelled out a few hundred bucks for both the Day Pass (which can range from $40-$70 depending on the time you book) and a couples massage. The Day Pass requires you check in at a specific time, but you can hang out as long as you want, so it was incredibly crowded, with bodies lining the perimeter of all three pools, lounging prone on its heated marble slabs, and lurking in the dark recesses of its three saunas.
I haven’t been back since the spa transitioned to its new bitcoin baths. Kotaku reached out to Bathhouse for comment, but until I hear back I think I’ll hold off on returning.