The facility is expected to supply approximately up to 525,000 MWh of heat annually – sufficient to meet the heating needs of approximately 70,000 apartment homes in Helsinki. Operations are currently scheduled to begin during next year.

The agreement represents an important milestone in the commercial deployment of OnZero’s AI Heat Factory design, which combines high-performance AI computing infrastructure with the recovery and productive use of the heat generated by computing operations.

“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.

Turning compute heat into a usable energy resource

OnZero’s AI Heat Factory is based on a liquid-cooled architecture designed around heat recovery from the outset. While conventional data centres frequently release the heat generated by their servers into the environment, OnZero’s systems are designed to capture up to 99% of compute heat and make it available at temperatures suitable for district heating networks.

Helen has been using waste heat from data centres in its district heating system since 2010 and contributes extensive experience in integrating recovered heat into Helsinki’s energy infrastructure. Each megawatt-hour delivered can reduce the need for fossil fuel-based heat in Helen’s system.

“Helen can utilise waste heat recovered from OnZero’s data centre in Helsinki’s district heating system. This provides a cost-effective way to reduce the need for combustion-based heat production while helping to ensure that district heating remains a competitive and attractive heating solution for customers in the future. Our goal is to phase out combustion-based energy production by 2040, and the utilisation of waste heat plays an important role in supporting this transition,” said Tuukka Toivonen, COO, Strategy and M&A at Helen.

Impact on the Environment

OnZero data centers are designed for zero on-site water consumption: heat is rejected to district heating networks rather than through evaporative cooling, so the internal closed-loop coolant is cooled without any water loss.

Where recovered heat replaces natural gas-based heat production, emissions reductions may amount to approximately 1,500 tonnes of CO₂ per MW of installed heat recovery capacity annually.

Reference project for further deployment

The design of OnZero’s AI Heat Factory is intended to enable deployment in locations where growing demand for AI computing capacity coincides with access to district heating networks or other users of recovered heat such as the manufacturing sector. The project is also expected to serve as a reference for the company’s planned expansion into additional European countries.

Photo credit: Arrak Arkkitehdit Oy. Artist’s impression.

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At full operation, the facility produces approximately 20 GWh of thermal energy annually, meeting around 75 percent of Söderkullan’s district heating demand. For a single facility, that is a substantial share of an area’s entire heating supply, delivered from heat that conventional data centers would discharge into the atmosphere. For Keravan Energia, it means a controllable, continuous heat source running year-round, reducing the utility’s reliance on combustion-based production in line with its clean transition strategy.

Zero waste is not a slogan at OnZero. It is the engineering principle the company was founded on. Every megawatt of compute capacity deployed has a destination for its heat. In a region where utilities are under growing pressure to replace combustion-based heat with clean alternatives, and where the demand for AI compute infrastructure is accelerating in parallel, that principle puts OnZero in an unusual position: a company whose core product becomes more valuable precisely when both pressures peak at the same time. The Helsinki metropolitan region is that moment, and Sipoo is where it becomes concrete.

To see how much CO2 this project saves in real time, visit our Footprint section.

The Sipoo project is the first deployment of this kind within Keravan Energia’s service area. The utility has indicated that a successful outcome opens the door to replication across multiple sites in the region.

Keravan Energia’s full announcement is available on their website.

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