Construction of Europe's largest electric boiler plant reached an important milestone as the plant's main transformers arrived in Hanasaari, Helsinki. Helen's upcoming plant will be able to meet the district heating needs of two areas the size of Lauttasaari, using electricity produced in a carbon-neutral way. AINS Group and Elomatic are carrying out the project as Helen's EPCM partners.
Europe's largest 200-megawatt electric boiler plant, along with its associated heat storage tanks, is currently under construction in the Hanasaari energy block in Helsinki. The project reached one of its key milestones this week, when its two high-capacity main transformers – each weighing more than 100 tonnes – arrived via special transport and were moved into place inside the plant building.
As Helen's partner, the AINS Group and Elomatic consortium is comprehensively responsible for the investment's overall project management, design and procurement, site management and supervision.
The electric boiler plant consists of four 50-megawatt electric boilers and two heat storage tanks. The boilers raise the temperature of water to a level suitable for the district heating network at times when electricity is sufficiently available and inexpensive. Installation of the four boilers was completed in April, inside a plant building that topped out over the winter.
– The key equipment has now been delivered to the plant. The massive transformers have been hauled into place, and we can now focus on continuing the pipework and electrical installation work needed to connect the main transformers. Once the installation and inspection work is complete, the commissioning phase will begin, during which an intensive test programme will be carried out, says Pekko Pennanen, EPCM project manager at AINS Group.
– The large power transformers weigh a great deal, and transporting them successfully was critical, since the delivery time for this type of transformer is very long. Once the transformers have been installed, several tests will be carried out to demonstrate that they can be safely energised. The transformer converts the voltage from 110 kilovolts to 10 kilovolts, meaning this is high-voltage equipment, says Karl-Gustav Pihl, design manager for electrical engineering at Elomatic.
Electric boiler plant adds flexibility to heat and electricity production
The plant includes two heat storage tanks containing district heating water, with a combined capacity of 1,000 megawatt-hours; these are still under construction. Heat can be stored in these "heat batteries" and used later to heat homes and buildings in Helsinki.
The combination of electric boilers and heat storage is designed to even out fluctuations in both heat and electricity production and pricing. Construction work on the plant began in summer 2025.
The transition to carbon-neutral, wind-powered energy has been highly visible in concrete terms at the Hanasaari construction site and the former coal power plant area throughout the project: the coal piles are gone, and Helsinki residents have been able to explore the area.
– Building a large-scale plant that produces district heat from electricity brings together several fields of engineering in a comprehensive and fascinating way. Carefully coordinating them and working in close collaboration has been – and will continue to be – essential to the project's success, Pennanen says.
The Hanasaari electric boiler plant, which has progressed on schedule, will be commissioned during the 2026–2027 heating season. The plant is part of Helen's goal to phase out combustion-based energy production by 2040.
Hanasaari electric boiler plant in numbers
- Europe's largest electric boiler plant
- Total capacity: 200 MW
- Consists of four electric boilers, 4 x 50 MW
- Two power transformers, each weighing over 100 tonnes
- Two heat storage tanks (so-called "heat batteries"), with a combined capacity of around 1,000 MWh. The tanks are around 40 metres tall.
- In cold weather, when electricity is affordable, the plant can produce almost 10% of Helsinki's district heat.
- The electric boilers replace the combustion of fossil and renewable energy sources, reducing emissions.
Further information:
Anu Kuoppamäki, executive vice president, AINS Group
tel. +358 50 341 1360
Karoliina Joensuu, industry business unit director, Elomatic
tel. +358 50 412 0546
