Helsinki Plans to Use AI Data Center Heat for 70,000 Apartments
Helsinki is preparing to use heat generated by artificial intelligence computing to supply its district heating network. Under an agreement announced on August 31, 2026, Finnish energy company Helen will integrate recovered heat from a planned OnZero data center into the system that distributes heat to homes and other buildings across the city.
Helen expects heat recovery to begin in 2027 and says the facility could supply more than 500,000 megawatt-hours annually once fully operational. The estimated contribution would be equivalent to the heating needs of around 70,000 apartments. These figures describe the project’s anticipated capacity, rather than heat already being delivered or a confirmed number of connected households.
OnZero gives a more specific upper estimate of 525,000 megawatt-hours per year. Its Finnish subsidiary, OnZero Finland Oy, signed the agreement with Helen. The subsidiary belongs to Vienna-based OnZero Alpha Holdings GmbH.
Recovering Heat at the Source
Data centers require cooling to prevent servers and other equipment from overheating. Much of the electricity consumed by computing equipment becomes heat, creating an opportunity to recover energy that would otherwise be released into the surrounding environment.
OnZero calls its proposed design an “AI Heat Factory.” According to the company, it uses liquid cooling and incorporates heat recovery from the outset. The systems are designed to capture up to 99% of compute heat and make it available at temperatures suitable for district heating networks.
OnZero also says its data centers are designed for zero on-site water consumption for cooling. Its approach uses a closed coolant loop and transfers heat to district heating networks instead of relying on evaporative cooling. Both the recovery percentage and water performance are company design claims, rather than published operating results from the planned Helsinki facility.
District heating provides a shared distribution system for recovered energy. Instead of each building producing all its heat independently, a network carries thermal energy from supply facilities to multiple users. This allows a large heat source, such as a data center, to serve demand beyond its immediate premises.
Supporting Helsinki’s Heating Transition
The agreement forms part of Helen’s broader shift in heat production. The company has already phased out coal and is investing in electric boilers, heat pumps, renewable energy and storage. Its climate transition plan, published in April 2026, also identifies data center heat recovery as a measure supporting the move away from combustion.
Helen aims to reduce emissions from its own energy production and the energy it sells by 77% by 2030, compared with a 2019 baseline. Its longer-term objective is to phase out combustion-based energy production by 2040.
The OnZero project therefore adds a potential heat source to an existing transition strategy. Helen has incorporated data center waste heat into Helsinki’s district heating system since 2010, giving it experience in connecting computing facilities with urban energy infrastructure.
A separate partnership with Telia illustrates this approach. Helen and Telia have supplied recovered heat from the Pitäjänmäki data center to the district heating network since early 2023. In May 2025, they announced an expansion with heat output equivalent to the needs of 14,000 two-room apartments, alongside plans to increase that figure to 28,000 in the future. These are separate from the OnZero project’s estimates.
Growing Electricity Demand Remains a Challenge
Heat recovery is becoming more relevant as digital infrastructure expands. In its 2026 update, the International Energy Agency (IEA) estimated global data center electricity consumption at 485 terawatt-hours in 2025 and projected approximately 950 terawatt-hours by 2030. AI-focused facilities are expected to increase their electricity consumption faster than the sector overall.
Recovering heat can improve the useful energy obtained from that electricity. It can also reduce the need to produce an equivalent amount of heat elsewhere. However, the data center still requires power to operate.
The climate benefit consequently depends on the electricity supplying the facility, the energy needed to recover and transport heat, and the heating source displaced. Replacing fossil fuel heat offers a different emissions outcome from replacing another low-carbon source. These are assessment considerations, rather than measured results for the Helsinki project.
Location and Seasonal Demand Shape the Opportunity
Access to heat customers is central to the model. The IEA identifies data centers near urban areas as promising sources for district heating and explains that heat pumps can raise lower-temperature recovered heat to suitable distribution temperatures. Modern networks operating at lower temperatures can also integrate a wider range of sources.
Seasonal balancing presents another practical issue. Computing can generate heat throughout the year, while building heating demand changes with the weather. The IEA highlights thermal storage as one way to retain surplus heat for later use, including seasonal storage being developed in Helsinki.
For developers and utilities, the project points to the value of assessing electricity supply, cooling, and potential heat customers together when planning new facilities. Its performance will ultimately be judged by actual heat delivered, operating reliability, and the energy production displaced as the facility enters service and increases output.
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