OnZero Partners with Helen to Link Helsinki AI Data Center to District Heating Network

Austrian AI data center developer OnZero Finland has signed an agreement with Finnish energy company Helen to connect its AI data center in Helsinki, Finland, to the city's district heating network. The partnership marks a significant step in the growing trend of data center heat reuse, where excess heat from computing infrastructure is repurposed for urban heating needs.

The facility is expected to supply the heat network with up to 525,000MWh of heat annually, an amount the companies say is equivalent to the heating requirements of 70,000 apartment homes in Helsinki. Operations are slated to begin sometime next year, positioning the project as one of the largest data center heat recovery initiatives in the Nordic region.

The deal forms a crucial part of OnZero's AI Heat Factory commercial deployment strategy. The design combines high-performance AI computing infrastructure with heat recovery technology, based on a liquid-cooled architecture. OnZero claims it can capture up to 99 percent of the heat generated by the data center and make it available at temperatures suitable for district heating networks, a capability that could redefine how data centers interact with local energy systems.

"We founded OnZero with a clear objective: to lower the cost of AI by combining high-performance AI infrastructure with the efficient recovery and productive use of compute heat. Our agreement with Helen demonstrates how this approach can work in practice – turning heat generated by AI computing into a valuable resource for Helsinki's district heating network," said Ali Siddiqui, CEO of OnZero.

OnZero also emphasized that its data centers are designed for zero on-site water consumption. Instead of using evaporative cooling, heat is rejected into district heating networks, allowing the internal closed-loop coolant to be cooled without any water loss. This waterless approach addresses a growing environmental concern in the data center industry, where water usage for cooling has come under increasing scrutiny.

The company said the project is expected to serve as a reference for its planned expansion into additional European countries. OnZero currently operates facilities in Kemijärvi and Kerava, Finland, and is developing new sites across the Nordic region and Europe. The company is headquartered in Vienna, Austria.

Helen, the Finnish energy firm, has signed several heat reuse agreements with data center companies in recent years. Most notably, it partnered with colocation giant Equinix, signing heat reuse agreements in 2024 and 2022. These deals underscore a broader industry shift toward viewing data centers not just as energy consumers, but as potential contributors to local energy infrastructure.

The Helsinki project highlights the growing synergy between AI infrastructure and urban sustainability goals. As AI workloads continue to expand, the ability to repurpose waste heat for community benefit could become a key differentiator for data center developers seeking to operate in densely populated areas with strict environmental regulations.