AI Data Centres Make Weak Promises on Waste Heat

Promises

• Headline potential: a January 2026 study by EnergiRaven and Viegand Maagøe says data-centre waste heat could warm 3.5 to 6.3 million UK homes by 2035. This is a theoretical figure that holds only "if the infrastructure is in place".

• Old Oak and Park Royal, west London: billed as a UK first, with £36m of government funding and heat from Vantage data centres for 9,000 homes (25,000 long term).

• Culham AI Growth Zone: reported as "may implement waste heat recycling".

Facts

• Operating today: only small schemes. Queen Mary University of London feeds its own campus heating, saving about £240,000 a year in gas. Deep Green has heated an Exmouth swimming pool since 2023.

• No homes yet: as of May 2026, no UK homes were heated by a commercial data centre via a district network. Old Oak was due to start construction in 2026 and go live in spring 2029.

• Culham is only a study: South Oxfordshire council commissioned a £105,600 feasibility study and says it cannot deliver the scheme itself. A third party would have to choose to build it.

• Next in line is small: Deep Green's 400kW unit at Urmston leisure centre was due to deliver heat from summer 2026. Its 5.6MW Bradford site has planning permission only.

Why the gap exists

• No pipes: heat networks supply only about 2-3% of UK heat, and a data centre can't afford to build one itself.

• Low-grade heat: it comes out at roughly 23-30°C and needs heat pumps (and more electricity) to reach 65-75°C.

• Low capture: realistic capture is 20-30% of the waste heat, against a theoretical 80%.

• Wrong location: large sites are often built away from housing, and heat doesn't travel far economically.

• No obligation: there is no national planning requirement to reuse heat, and Ofgem calls the regulation "an emerging area".

A fair test for any announcement is whether there is a named heat customer, a funded network, and a go-live date. Most UK announcements have none of the three.

I didn't confirm whether Old Oak construction has actually started, or find current performance figures for Exmouth or Urmston.