The internationally recognized AmbiHeat plant, built next to Savon Voima’s Joensuu power plant, was commissioned in December. The facility received the prestigious Heat Pump City of the Year award in autumn 2025.
Delivered by Calefa, the solution combines waste heat recovered from a flue gas scrubber with energy drawn from river water. The result is a highly flexible, emission-free heat production system that can be utilized throughout the year.
A solution of this kind has not previously been implemented anywhere in Europe. Even before completion, the Joensuu AmbiHeat plant was awarded the Heat Pump City of the Year title in Brussels in autumn 2025. The award is presented annually to a European heat pump project that truly pushes the boundaries of heat pump technology.
Now, the award-winning plant has moved from recognition to reality and is delivering heat in Joensuu.
District Heat Produced Automatically
Commissioning of the AmbiHeat plant began at the end of 2025. According to Jukka Varonen, Project Manager at Savon Voima, the process was well controlled.
“So far, the plant has produced some thousands of megawatt hours of district heat. The figure would be higher, but operation has been limited by high electricity prices and the Christmas holiday period.”
Electricity for the plant is purchased from the market, meaning operation is guided by price thresholds. The plant is run when market conditions are favorable. Thanks to modern and user-friendly heat pump technology, operation has remained reliable despite fluctuations in electricity prices.
“The plant is easy to start and stop based on electricity prices. It doesn’t require continuous supervision and operates very steadily,” Varonen explains.
With just under 300 operating hours, the plant has already proven its ability to efficiently recover condensate heat from the flue gas scrubber.
“We’ve already seen clear indications that the promised performance levels will be achieved. The plant is still in its run-in phase and has been operated at around 90 percent capacity.”
Two Heat Sources Enable True Year-Round Operation
During the heating season, the AmbiHeat plant utilizes condensate heat recovered from the flue gas scrubber. Heat pumps upgrade this waste heat directly into the district heating network, while simultaneously improving the efficiency of both the scrubber and the entire power plant.
This summer, Savon Voima takes a step in Joensuu that until recently had not been seen anywhere in Europe.
When the power plant boiler is shut down, AmbiHeat switches to river water as its heat source. This makes it possible to produce district heat during the summer months without any combustion-based generation.
“Using river water in summer is completely new for us. Naturally, it hasn’t yet been tested, as the river water temperature is still too low. River water operation will be tested as soon as conditions allow,” Varonen says.
In winter operation, the heat pump plant delivers approximately 6 MW of additional heat capacity to the Joensuu district heating network by enhancing the flue gas scrubber. In summer, output in river water mode is around 4–5 MW, covering a significant share of summer heat demand.
This ability to operate efficiently throughout the year is what makes the AmbiHeat solution technically and economically exceptional.
Built for International Impact
The Heat Pump City of the Year award, presented by the European Heat Pump Association (EHPA), evaluates projects as complete systems. Innovation, impact, scalability, and a meaningful role within the energy system are key criteria.
At the Joensuu AmbiHeat plant, all of these elements come together: two complementary heat sources, year-round operation, and a major role in covering both base load and summer load in the district heating network.
The award recognizes both Savon Voima’s bold investment and Calefa’s long-term commitment to advancing heat pump technology.
“At this stage, we’re very satisfied with the plant. In a year’s time, we’ll have more experience, and the overall performance can be assessed in even greater detail,” Jukka Varonen from Savon Voima concludes.
Savon Voima has received EU NextGeneration funding for the Joensuu AmbiHeat plant project.
Learn More About Electrified Heat Production with Two Heat Sources!
Petri Vuori
Toimitusjohtaja
+358 40 553 4427
petri.vuori@calefa.fi
