AI data centres reject almost all the electricity they consume as low-grade heat — and from 1 July 2026 Germany's Energy Efficiency Act (EnEfG) requires new data centres to reuse at least 10% of it, rising to 20% by 2028. Across the EU, recoverable data-centre waste heat is estimated at over 300 TWh a year by 2030 — comparable to a tenth of EU space-heating demand. Capturing it depends on moving hot water efficiently: well-insulated distribution is the difference between usable heat at the district network and loss to ambient.
Germany's Energy Efficiency Act makes waste-heat reuse a legal requirement for new data centres from 1 July 2026 — the first hard mandate of its kind in Europe. Denmark, the Netherlands and the EU Energy Efficiency Directive push the same direction. Heat that was vented is becoming an asset operators must capture.
| Project | What |
|---|---|
| Microsoft — Espoo, Finland | Up to ~250,000 homes' heat to Fortum district network (one of the world's largest DC heat-reuse schemes) |
| Google — Hamina, Finland | Sea-water cooling; waste heat reuse studied for local district heat |
| Stack Infrastructure — Denmark | Heat supplied to ~6,000+ homes via district heating |
| Equinix — multiple EU sites | Heat-export agreements with municipal district-heating operators |
Publicly announced data-centre heat-reuse projects. Figures as reported by operators/municipalities.
Low-grade data-centre heat is upgraded by heat pumps and piped to district networks. Every metre of that hot-water distribution — pipes, valves, heat-exchanger skids, buffer tanks — loses heat to ambient unless it is properly insulated. For a 30-45 °C source, even modest distribution losses erase the margin that makes reuse economic. Removable insulation on the distribution side is what keeps recovered heat usable at the customer.
| Country / framework | Requirement | From |
|---|---|---|
| Germany — EnEfG | ≥10% waste-heat reuse (≥20% from 2028) | 1 Jul 2026 |
| EU — Energy Efficiency Directive | Reporting + reuse where cost-effective | In force |
| Denmark | Tax reform lets data centres sell heat to district networks | In force |
| Netherlands | Heat-reuse expectations written into permitting | In force |
National efficiency law texts + EU EED. The hard numeric trigger is Germany's EnEfG.
| Typical temperature | |
|---|---|
| Data-centre waste heat (air/water cooling) | ~30-45 °C |
| District-heating supply temperature needed | ~60-80 °C |
| Gap closed by | heat pumps + insulated distribution |
Low-grade DC heat must be upgraded by heat pumps and then moved without loss — every °C lost in distribution piping erases the margin that makes reuse economic.
Every gas turbine, HRSG and steam line in this fleet — and every kW of data-centre waste heat — is a hot surface. Inzonex modular removable insulation cuts surface heat loss up to 96% while keeping flanges accessible for maintenance.
See Inzonex modular insulation →Yes — under the Energy Efficiency Act (EnEfG), data centres commissioned from 1 July 2026 must reuse at least 10% of their waste heat, rising to 20% for those from 2028.
Estimates put recoverable EU data-centre waste heat above 300 TWh/year by 2030 — on the order of 10% of EU space-heating demand — though realised reuse depends on proximity to district-heat networks.
Data-centre heat is low-grade (~30-45 °C), so it needs heat pumps to upgrade and efficient, well-insulated distribution to reach district networks without losing the heat en route.
German EnEfG (Energieeffizienzgesetz) data-centre provisions; EU Energy Efficiency Directive; operator/municipal announcements (Microsoft Espoo, Stack Denmark, Equinix). EU 300 TWh potential: industry/IEA estimates. Author: Dmytro Aheiev (ORCID 0009-0001-5512-0291). Externally-sourced figures attributed; not Inzonex estimates.
Externally-sourced figures are attributed and link to primary sources; deal terms are public company/trade-press announcements. Author: Dmytro Aheiev (ORCID 0009-0001-5512-0291).