Summary

• OnZero has agreed to connect a planned AI computing facility to Helen’s Helsinki district-heating network.
• The company expects the site to supply up to 525,000 MWh of recovered heat annually once operations begin.
• The project tests whether data-centre waste heat can become dependable urban energy infrastructure rather than an unused by-product.

A planned Helsinki AI-computing facility is being designed as part of the city’s heating system rather than merely another large electricity consumer, after OnZero agreed to connect the site to the district-heating network operated by Finnish energy company Helen.

The Vienna-headquartered infrastructure company expects its AI Heat Factory to provide up to 525,000 MWh of recovered heat each year, which it says would correspond to the heating requirements of roughly 70,000 apartment homes. Operations are currently scheduled to begin during 2027.

OnZero’s design uses direct liquid cooling and is intended to capture heat produced by computing equipment before transferring it into Helsinki’s heating network. The company claims its facilities can recover up to 99% of compute waste heat, although the Helsinki figures describe expected performance from a plant that has yet to enter operation.

Helen already uses recovered energy as part of its district-heating system, giving the project an existing utility customer and network rather than requiring a new market for low-temperature heat to be created around the data centre. That distinction can determine whether technically recoverable energy becomes commercially useful.

Heat recovery depends on the city around it

Every data centre ultimately turns much of the electricity consumed by computing equipment into heat, but capturing that thermal energy is only the first step. A viable recovery project also needs customers close enough to use it, pipework and heat exchangers capable of transferring it economically, suitable temperatures, and demand that broadly coincides with when computing infrastructure is producing the heat.

Helsinki offers unusually favourable conditions because district heating is already deeply embedded in the city’s energy system. Finland has also become a testing ground for how large computing facilities fit into electricity and heating networks, an issue Techopia explored in Finland becomes a test bed for AI’s power problem.

The OnZero project pushes that relationship further by designing the compute facility around heat recovery from the outset. Instead of treating thermal output as a waste-management problem to solve after servers have been installed, the company is attempting to make the heating connection part of the site’s operating model.

That approach is becoming more relevant as European policy increases scrutiny of data-centre efficiency and waste heat. Large facilities face growing expectations to examine heat-recovery options where technical and economic conditions allow them, moving the issue from sustainability reporting towards engineering, planning, and utility negotiations.

AI infrastructure acquires a second product

A successful system effectively gives the data centre two outputs: computing capacity for digital customers and heat for the local energy network. The second does not erase the electricity consumed by the first, but it can improve the overall use made of energy that would otherwise be rejected through cooling equipment.

Whether that creates a durable business model depends heavily on local conditions. District-heating systems are common in parts of northern Europe but far less widespread elsewhere, while seasonal heat demand can leave summer output with fewer customers precisely when computing workloads remain high.

The quality of the heat matters as well. Server-cooling systems can produce temperatures below those traditionally used in urban heat networks, which can require heat pumps or other equipment before recovered energy becomes useful. Those systems consume electricity themselves and add capital and maintenance costs to the project.

OnZero operates existing facilities in Kemijärvi and Kerava and says it is developing further sites across the Nordic region and Europe. Helsinki will offer a larger demonstration of whether an infrastructure model built around liquid cooling and heat sales can move from specialist projects into the broader AI data-centre market.

For Helen, the arrangement fits a heating system already shifting towards electricity, heat pumps, and recovered energy as combustion plays a smaller role. The utility has set a target of phasing out combustion-based energy production by 2040, making externally supplied waste heat potentially useful where it can be delivered reliably and at a competitive cost.

The economics still have to survive contact with an operating plant. OnZero’s 525,000 MWh figure is an expectation rather than a measured output, while future heat demand, computing utilisation, electricity prices, network conditions, and the completed engineering design will all affect the amount of usable heat that actually reaches customers.

Even with those qualifications, the project demonstrates how the physical consequences of AI investment are becoming embedded in other infrastructure systems. Data centres need power, cooling, land, and network connections, but in cities with extensive heating networks they can also become energy suppliers — provided the economics work well enough for utilities to depend on the heat rather than merely count it in an environmental report.