Finland’s capital is about to switch on a heating system unlike anything built before. Helsinki is installing the world’s largest air-to-water heat pump — a machine capable of warming 30,000 homes using only renewable electricity, even when outdoor temperatures plunge to -4°F (-20°C). The project, led by Finnish energy company Helen Oy and built by MAN Energy Solutions, is expected to begin operations during the 2026 C.E.–2027 C.E. heating season.
At a glance
- Air-to-water heat pump: The Helsinki installation will have a full heating capacity ranging from 20 to 33 MW depending on air temperature, making it the largest of its kind anywhere in the world.
- Carbon emissions savings: Combined with 50 MW boilers, the system will deliver 200 GWh of heat annually — cutting roughly 26,000 tonnes of CO2 emissions each year compared to fossil fuel-based heating.
- CO2 refrigerant: Unlike most heat pumps that rely on environmentally harmful gases, this system uses carbon dioxide as its refrigerant, allowing it to deliver heat at temperatures up to 194°F (90°C).
Why Helsinki is going big on heat pumps
District heating — a centralized system that produces heat in one place and pipes it underground to homes and businesses — is already widely used across Finland and much of northern Europe. It is one of the most energy-efficient ways to heat dense urban areas. The problem has always been the fuel source.
According to the International Energy Agency, roughly half of Finland’s heating and cooling energy currently comes from biomass. That is cleaner than coal or gas, but it still produces emissions. Helsinki has committed to becoming carbon-neutral by 2030 C.E., and the city’s district heating network is central to that plan.
“Helsinki has set the ambitious goal to become carbon neutral by 2030, and transitioning our heating system is crucial to achieving this,” said Juhani Aaltonen, VP of Green Investments at Helen Oy.
The new heat pump gives the city a way to run that network on wind and solar power instead of combustion — at scale, and reliably through Arctic-level winters.
How the technology works
A heat pump does not generate heat the way a furnace does. It moves heat — drawing low-temperature thermal energy from the outdoor air and raising it to a usable level using electricity. The result is a system that can deliver more energy as heat than it consumes as electricity, making it fundamentally more efficient than burning fuel.
What makes the Helsinki installation unusual is its engineering. The compressor unit uses a high-speed motor with active magnetic bearings, meaning it operates without a dry gas seal system or oil lubrication — a design that reduces maintenance needs and increases reliability in cold climates. MAN Energy Solutions, the German manufacturer behind the system, says the CO2 refrigerant can deliver consistent performance even when outdoor air temperatures fall to -20°C, conditions that would challenge many conventional heat pump designs.
The electricity powering the pump can be sourced from wind and solar, completing the clean-energy loop. And because output can be adjusted based on outdoor temperature and demand, the system is also expected to bring more pricing stability to customers — something district heating networks have not always been able to offer.
A model for cold-climate cities worldwide
Helsinki is not the only cold city watching this project. District heating networks are common across Scandinavia, Central Europe, and parts of Asia, and many of them still burn fossil fuels or biomass. A proven large-scale heat pump system that works reliably at sub-zero temperatures could offer a credible upgrade path for dozens of cities.
“Urban district heating projects that utilize climate-neutral technologies are essential for advancing global efforts to reduce carbon emissions,” said Uwe Lauber, CEO of MAN Energy Solutions. “We are excited to see our heat pump solution play a key role in driving the energy transition forward.”
The Helen Oy heat pump project is one of several major investments the company is making to decarbonize Helsinki’s energy system ahead of the city’s 2030 C.E. deadline. Earlier investments include large-scale seawater heat pumps already operating in the city.
What still needs to happen
The heat pump has not yet begun operations — the 2026 C.E.–2027 C.E. timeline means the most important test, a full Finnish winter, is still ahead. Scaling a technology from pilot size to world-record capacity always carries engineering unknowns. And while 26,000 tonnes of annual CO2 savings is significant, Helsinki’s full decarbonization plan will require many more projects of similar ambition to reach its 2030 C.E. goal.
Still, this installation represents something cities in cold climates have long needed: evidence that district heating networks can go fully renewable without compromising reliability. If it performs as designed through Helsinki’s winters, it will be difficult to argue the technology cannot scale. Other cities will be watching very closely.
The broader context matters too. The IEA has identified heat pumps as one of the most critical technologies for meeting global climate targets, with installations needing to roughly triple by 2030 C.E. Projects like this one — large, cold-climate, fully renewable — help establish what that future can actually look like.
For Finland, a country that has long been a quiet leader in clean energy innovation, the Helsinki heat pump is another step in a tradition of practical climate ambition. For the rest of the world, it is a proof of concept worth watching.
Read more
For more on this story, see: Interesting Engineering
For more from Good News for Humankind, see:
- Alzheimer’s risk cut in half by drug in landmark prevention trial
- Ghana establishes marine protected area at Cape Three Points
- The Good News for Humankind archive on Finland
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