OnZero and Helen Partner on AI Heat Factory in Helsinki
OnZero, a data centre developer, and Helen, Helsinki's energy company, formalised an agreement to construct an AI Heat Factory. Scheduled for operation by 2027, the facility projects up to 525,000 megawatt-hours of heat annually, sufficient for approximately 70,000 apartments. Liquid-cooled servers will capture heat; industrial heat pumps raise it to 95 degrees Celsius for Helsinki's district heating network.
OnZero sells heat to Helen, gaining an income source. Helen anticipates lower costs than burning wood or gas, aiming to cease all combustion by 2040. This plant is expected to meet about nine per cent of Helen's 2024 heat sales. Finland's electricity grid primarily uses nuclear, wind, and hydropower.
But, this initiative proposes data centre waste heat as a valuable resource. Electrons power AI chips; captured hot water channels through pipes to warm homes. Most data centres typically expel this excess heat into the atmosphere.
Servers convert nearly all electricity drawn into heat, requiring additional power for cooling. Many data centres use cooling towers, consuming vast water; Forbes reported Google's largest United States data centre used 4.92 billion litres in 2025. United States data centres consumed 4.4 per cent of electricity in 2023, potentially reaching 12 per cent by 2028, per Lawrence Berkeley National Laboratory. OnZero proposes selling this generated heat.
Finland widely employs district heating. Helen, a major provider, requires up to 2.5 gigawatts of heat during winter. Its last coal plant decommissioned in 2025, it now relies on heat pumps, electric boilers, and wood.
And, this domestic heat supply offers a security advantage. Russia halted gas exports to Finland in May 2022, making electricity-generated heat independent. Olli Sirkka, Helen's chief executive, noted data centre heat is usually wasted. Helen has integrated waste heat since 2010; OnZero increases this scale significantly.
OnZero's liquid-cooled servers extract heat at 50 to 60 degrees Celsius. Industrial heat pumps elevate this to 95 degrees Celsius for the district network. This removes the need for evaporative cooling towers. OnZero states its patented Whisper software manages efficiency.
OnZero owns the facility, leasing space to Big Tech and artificial intelligence organisations. The Helsinki project, 120 megawatts, is estimated at USD 1 billion. OnZero operates two smaller sites in Finland. Skeptics question data centre electricity demands, citing grid strain.
Ali Siddiqui, OnZero's chief executive, argues Helen would consume electricity for alternative heating regardless. But, an OnZero plant uses electricity twice: for AI chips, then passing heat to Helen. This dual-use model draws from the grid portion replacing fossil heat, contingent on existing heat demand.
But, electricity consumption by the heat pumps themselves also faces scrutiny. OnZero states it captures up to 99 per cent of server heat. However, raising water to 95 degrees Celsius requires power. The company indicates its heat pumps deliver approximately five units of heat for every unit of electricity used.
During summer, when heating demand falls, Helsinki's network supplies hot water. Surplus OnZero heat goes to dry coolers. OnZero is negotiating tenancy agreements for the new plant. Microsoft also develops data centres in the region, which utility Fortum plans to utilise.
Helen's financial performance supports the project's viability. Since abandoning coal, Helen has reduced district heating prices for three consecutive years, returning to profitability. And, Olli Sirkka confirmed OnZero heat costs less than burning wood or gas. The project, if successful, establishes data centre waste as a municipal fuel source.
Helsinki's energy company Helen and data centre developer OnZero will build an AI Heat Factory.
The facility, operational by 2027, will supply heat for approximately 70,000 apartments.
OnZero will generate revenue from leasing data centre space and selling recovered heat to Helen at a lower cost.
The project aims to reuse electricity, powering AI chips first, then converting waste heat for district heating.
Concerns regarding electricity consumption and heat pump efficiency have been addressed by both companies.
Source: Forbes
