A washing-machine-sized data centre heats a UK pool. £200 million is now behind it
Deep Green's mineral oil-cooled servers have been quietly warming a Devon pool since 2023. Octopus Energy just backed the idea with £200 million, a US expansion, and a plan for 150 more pools.
Waste heat from AI servers now warms UK pools, and Octopus Energy just bet £200 million it scales.
A UK swimming pool has been heated by a data centre the size of a washing machine since 2023. Three years later, Octopus Energy has put £200 million behind scaling that idea to 150 more pools, plus a data centre build in Michigan.
One box, one pool, free heat
Exmouth Leisure Centre in Devon heats its pool with a data centre the size of a washing machine. The servers inside sit submerged in mineral oil, which pulls heat off the chips and warms the pool water to about 30 degrees Celsius for roughly 60% of the time. The startup behind it, Deep Green, installs the hardware for free and reimburses the centre's electricity bill. It makes its money selling the spare computing capacity to AI and machine learning clients elsewhere.
Pools needed the help
UK pools had a rough few years before this deal. The BBC reported that 65 public swimming pools closed between 2019 and 2023, mostly over energy costs. Sean Day, who manages the Exmouth centre, said he had budgeted for a £100,000 jump in his energy bill before Deep Green stepped in, calling the past 12 months of costs "astronomical." Swim England's chief executive, Jane Nickerson, welcomed pools "embracing innovative solutions."
The part that doesn't scale to everything
Cambridge engineering professor Julian Allwood says the idea holds up. Data centres generally use less energy than people assume, he says, but the biggest ones still need billions of gallons of water and cost millions to cool, which is why some now sit underwater, in old mines, or inside the Arctic Circle. Cities in Denmark and Sweden already pipe data centre heat into thousands of homes. Deep Green's version only works at this small, modular scale, sited right next to the pool that needs the heat. It doesn't touch how much water or power a hyperscale data centre burns through to stay cool.
Data centres have got a huge problem with heat.
Three years on, real money showed up
Deep Green has since paired with Zendo to heat the pool at Move Urmston, a leisure centre in Trafford, the second UK site running on data centre waste heat. The operator says it now saves about £80,000 a year and cuts its carbon footprint. Octopus Energy, the UK energy supplier, has put £200 million behind Deep Green with a plan to reach as many as 150 more pools. Deep Green is also building its first US site, a 24-megawatt data centre in Lansing, Michigan, aiming to go live in the first half of 2027, part of a target of 300 megawatts of distributed capacity across Europe and the US.
Why a build studio cares
Every workload we deploy for a client runs on somebody's servers, and those servers throw off heat whether anyone reroutes it or not. Deep Green's whole business is deciding that byproduct is worth piping somewhere useful instead of venting it. It's the same question behind picking a hosting region or a database tier for a client build: where does the waste actually go, and does anyone downstream get to use it.
Next step: the original pilot is covered by the BBC. For the 2026 scale-up, see Data Center Dynamics on the Michigan build, or The Next Web on the Octopus Energy funding. If you are choosing a hosting region or a database tier for a build and want to think through where the byproduct actually goes, write to us at hello@gattyworks.com.