Helen Oy - Heat-pump system that recovers data center waste heat for district heating networks

Helsinki · Finland · 2010 · Helen Oy — Helsinki's municipally-owned energy company and operator of the city's district heating network.

Running continuously since 2010 and repeatedly expanded (2022 Equinix extension plus the separate Elisa agreement; a further Equinix extension in 2024), the Helen model has moved well past a pilot stage into a durable, recontracted commercial service. Its logic has since been replicated at metropolitan scale: the Fortum–Microsoft heat-pump plants, backed by roughly €225 million of investment (including EU NextGenerationEU funding and Finnish government support), started operations in May 2026 and are expected to eventually supply close to 40% of all district heat used by around 250,000 residents and businesses in the Espoo/Kirkkonummi area — a shift from single-building heat-recovery deals to a heat source that shapes an entire regional energy system. The project also reframes data centers, typically viewed only as large energy consumers, as active contributors to public infrastructure, a narrative now being used by Finnish authorities and utilities to support further decarbonization of urban heating.

Highlight

The world's first data-center-to-district-heating project — running in Helsinki since 2010 — has grown into a metropolitan-scale model in which hyperscale data centers are expected to supply up to 40% of the district-heating demand of a quarter-million residents in the neighbouring Espoo-Kirkkonummi area.

Extended description

• Context and problem: data centers reject large volumes of low-grade heat (roughly 25–35°C) as a by-product of continuous server cooling; historically, this heat has simply been dissipated into the atmosphere as an energy loss, while cold-climate cities such as Helsinki carry a large, sustained, fossil-fuel-dependent district-heating load. The challenge addressed by this model is not generating new energy, but recovering an existing waste stream and routing it into an energy system that already needs it — a district-heating decarbonization strategy that also seeks to progressively phase out coal and gas from urban heating.

• How it works: heat rejected by data-center cooling systems is captured through heat exchangers and fed to industrial heat pumps operated by the district-heating utility, which raise its temperature from roughly 25–35°C to the 65–90°C required for distribution. The heated water is then injected into the existing district-heating network, which already reaches homes, offices and public buildings, and the whole chain is automated and optimized to track real-time heating demand. In Helsinki, Helen's partnership with Equinix — the world's first project of this kind — began at the Kanavaranta substation in 2010 and was extended in 2022 (Suvilahti HE3 and Viikinmäki HE5) and again in 2024, when the Viikinmäki extension alone was sized to cover the annual heating demand of roughly 1,000–1,500 homes; Elisa's Helsinki data centre joined the model the same year in 2022. In the neighbouring Espoo/Kirkkonummi area, Fortum built two large heat-pump plants — Hepokorpi (Espoo) and Kolabacken (Kirkkonummi) — comprising 40 air-to-water and 72 water-to-water heat pumps with up to 180 MW of district-heating capacity, 200 MW of electric-boiler backup and 800 MWh of thermal storage, to capture waste heat from two new Microsoft hyperscale data centers; the plants started operating in May 2026 using ambient air as their heat source, with Microsoft's data-centre waste heat scheduled be phased in as the facilities come online.

• Technologies, stakeholders and operational logic: the model depends on mature, proven components — heat exchangers and industrial heat pumps — rather than novel generation technology, which lowers technical risk. It requires close public–private collaboration between a municipal or utility-owned district-heating operator (Helen, Fortum) and data-centre operators (Equinix, Microsoft and telecom operator Elisa), and is only viable where a centralized district-heating network already exists and a cold climate guarantees sustained heating demand year-round. The Fortum–Microsoft plants represent an investment of roughly €225 million, supported by NextGenerationEU funding and Finnish government grants, reflecting the scale of capital required to move from single-building heat-recovery deals to a metropolitan supply model.

• Systemic implications: the model turns data centers from pure energy consumers into active nodes of the urban energy system, and — at the scale now being reached in the Helsinki metropolitan area — can materially reshape city-level energy planning: once fully ramped up, data-centre waste heat is expected to cover close to 40% of the roughly 2 TWh annual district-heating demand of about 250,000 heat users in the Espoo/Kirkkonummi network, reducing reliance on fossil-fuel peaking plants and displacing an estimated several hundred thousand tonnes of CO2 emissions per year across the completed projects.

Demonstrated metrics

• World's first data-center district-heating project: Helen and Equinix, Kanavaranta substation, operating continuously since 2010.

• 2022 extension: additional Equinix data centers (Suvilahti HE3, Viikinmäki HE5) plus a separate Elisa data-centre heat-export agreement, both in Helsinki.

• 2024 extension: further waste heat from Equinix (Viikinmäki), sized to meet the annual heating demand of roughly 1,000–1,500 one-bedroom-equivalent homes.

• Fortum–Microsoft plants (Espoo/Kirkkonummi): ~€225 million investment; 40 air-to-water + 72 water-to-water heat pumps; up to 180 MW district-heating capacity, 200 MW electric-boiler capacity, 800 MWh thermal storage; operational start May 2026.

• Once fully ramped up, data-centre waste heat is expected to cover up to ~40% of the ~2 TWh annual district-heating demand of ~250,000 heat users in the Espoo/Kirkkonummi network.

Real impact

Running continuously since 2010 and repeatedly expanded (2022 Equinix extension plus the separate Elisa agreement; a further Equinix extension in 2024), the Helen model has moved well beyond the pilot stage to become a durable, recontracted commercial service. Its logic has since been replicated at metropolitan scale: the Fortum–Microsoft heat-pump plants, backed by roughly €225 million in investment (including NextGenerationEU funding) and Finnish government support), started operations in May 2026 and are expected to eventually supply close to 40% of all district heat used by around 250,000 residents and businesses in the Espoo/Kirkkonummi area — a shift from single-building heat-recovery deals to a heat source that shapes an entire regional energy system. The project also reframes data centers, typically viewed only as large energy consumers, as active contributors to public infrastructure, a narrative now being used by Finnish authorities and utilities to support further decarbonization of urban heating.

Implementation location and date

Helsinki, Finland — Kanavaranta district-heating substation, operational since 2010; extended to the Suvilahti and Viikinmäki (Equinix) data centers in 2022 and 2024, and to an Elisa data centre in 2022. Espoo and Kirkkonummi municipalities (greater Helsinki metropolitan area) — Hepokorpi and Kolabacken heat-pump plants, operational since May 2026, tied to new Microsoft data centers. All deployments are fully commercial, contracted infrastructure rather than pilots, although the Espoo–Kirkkonummi project is still ramping up as Microsoft's facilities come online.

Similar cases elsewhere

Stockholm, Sweden — Stockholm Exergi's "Open District Heating" marketplace (launched 2014) lets data centers and other industrial heat sources sell surplus heat into the city's district-heating network under standardized, temperature-indexed contracts; more than 30 data centers from more than 16 providers are now connected, recovering enough heat to warm around 11,000 apartments. Paris, France — Equinix's PA10 data center supplies heat (recovered at 28°C and raised to 65°C by three heat pumps) to the Paris 2024 Olympic Aquatic Centre pools and roughly 600 neighbouring homes and businesses, free of charge for 15 years, showing the model adapting to a temperate, non-Nordic climate and to a landmark public facility rather than only housing. Together, these cases show the Nordic-pioneered "data center as heat source" model already being replicated across Northern and Western Europe; broader replication in warmer climates or the Global South remains limited, since it depends on pre-existing centralized district-heating infrastructure and strong, sustained heating demand — conditions that are rare outside temperate or cold-climate cities.

Sources

• Helen — Heat recovery service for data centers: https://www.helen.fi/en/companies/cooling-for-companies/Heat-recovery-service-for-data-centers

• Helen — More Helsinki homes heated by Equinix waste heat (2024): https://www.helen.fi/en/news/2024/more-Helsinki-homes-to-be-heated-using-excess-heat-from-Equinix-data-centers