Steady Energy – Small modular reactors for district heating

Why?

More than 40 percent of Europe’s energy consumption is used for heating. Despite its significance, heating has been a largely overlooked sector in the energy transition. District heating networks already supply nearly 80 million Europeans, but the majority of their energy is still produced using fossil fuels. In 2020, VTT launched a research project to develop a nuclear reactor concept for district heating. Steady Energy was founded to develop and commercialize the small modular reactor designed at VTT specifically for district heating. Until now, nuclear power has been used almost exclusively for electricity production.

What and how?

The small LDR-50 reactor developed by Steady Energy is installed underground in bedrock. With a capacity of only 50 MW, the reactor cools itself passively without separate systems. Multiple reactors can be combined to form a suitably sized small nuclear plant. Because the plant is designed specifically for heat production, its construction costs, complexity, and technical risks are significantly lower than those of a conventional electricity-producing nuclear plant.

The design is a simplified version of the light water reactor, which has been used for decades. The innovation lies in the ability to produce heat competitively without state subsidies and safely in urban environments where district heating is needed. Finland offers excellent conditions for developing small nuclear plants, with strong nuclear expertise, extensive district heating networks, and broad public support for nuclear energy.

Growth and internationalisation

Steady Energy’s pilot plant will be built in Salmisaari, Helsinki. The reactor is otherwise identical to future commercial units, but during testing, electric heaters will be used instead of nuclear fuel. The goal is to complete the pilot plant by early 2027 and move towards the first commercial project by 2028. In addition to Helsinki, small modular reactors for district heating are also being planned in Kuopio.

The Finnish district heating network could accommodate an estimated 20–30 small nuclear plants. Internationally, the company’s growth focus is on other Nordic countries and Eastern Europe, such as Poland, where district heating is largely fossil-fuel based. Discussions are also underway with district heating providers in South Korea. Nuclear technology focused on heat production is also suitable as a heat source for certain industrial processes and for seawater desalination in regions suffering from a lack of fresh water. The European heating market is expanding because the EU aims to double low-emission district heating production by 2050.

The importance of growth equity

In July 2025, Steady Energy announced that it had raised EUR 32 million in growth funding to accelerate the development of its technology and international expansion. Investors in the round included 92 Capital, Lifeline Ventures, LähiTapiola, Valo Ventures, Move Energy – as well as Tesi, which participated with its first investment. The development and commercialization of small modular reactor technology would not be possible without long-term investors committed to transformative opportunities.

One of Tesi’s objectives is to invest in growth sectors around which innovation and expertise clusters can be built. Companies supporting the clean transition are an example of such a sector. Nuclear technology is a new area within cleaner energy solutions, in which Finland has the opportunity to become a global frontrunner.

General information

Steady Energy was founded in 2023 as a spin-off from a VTT research project. The company develops and commercialises simple heat-producing small modular reactor technology. Its goal has been to secure customer agreements even before the technology is fully commercialized, and the first agreements have already been signed. Steady Energy employs approximately 50 people, along with around 200 external nuclear experts from various sectors, and its headquarters is located in Espoo. To date, the company has raised a total of approximately EUR 50 million in growth funding for the development and commercialisation of its technology.