A year without coal also stood up to a freezing winter: emissions from Helsinki’s district heating fell by 56%, reliability of supply remained high and prices came down
Helen phased out coal a year ago when the Salmisaari B power plant was decommissioned. The first year without coal proved to be a real test due to the exceptionally cold winter, demonstrating that the renewed energy system works. In 2025, emissions from district heating production fell by 56%, reliability of supply remained above 99.9%, and the price of district heating decreased.
The winter’s exceptionally severe cold spells put the renewed energy system to a practical test. According to measurements from the Kaisaniemi weather station, January and February were colder than usual in Helsinki, but district heating was available to customers without interruption throughout the period.
“Finland’s first coal-free winter in Helsinki showed in practice that the system works. Even during the harshest cold spells, production met demand and customers’ heating remained reliably on,” says Timo Aaltonen, Senior Vice President, Heating and Cooling at Helen.
New forms of production replaced coal while also lowering the price of district heating
As recently as 2024, coal accounted for 21% of Helen’s district heating production. It has now been replaced in particular by heat pumps, electric boilers and biomass.
At Salmisaari, Helen commissioned a new electric boiler plant, an air-to-water heat pump plant and a heating boiler converted to run on pellets.
“We have modernised energy production faster than many believed possible. At the same time, we have significantly reduced emissions without customers having to compromise on reliability of supply,” Aaltonen says.
Phasing out coal has also affected the price of district heating. As expensive fuel and emission allowances are no longer needed to the same extent as before, the price of district heating has been reduced. At the same time, energy self-sufficiency and security of supply have been strengthened.
Next, even greater use of waste heat
The next phase in the renewal of district heating will focus in particular on making greater use of waste heat. The Eiranranta heat pump plant, due to be completed in the summer, will recover waste heat from wastewater and use it to produce district heating and district cooling.
Waste heat generated in the production process of the 3H2 hydrogen pilot plant being built in Vuosaari will also be recovered and fed into the district heating network when the plant comes on line at the end of 2026. In addition, Helen is exploring data centre projects whose waste heat could be utilised in district heating production.
In the longer term, Helen is also studying the potential of small modular nuclear reactors as part of combustion-free energy production by 2040.
“The district heating network is a flexible platform to which new forms of production can be connected as they are completed. When production is not based on a single fuel, the system is better able to withstand extreme weather,” Aaltonen concludes.