The idea of exploring an energy community in Marttila did not begin with a broad wish to do something greener or more innovative. It grew out of a practical need to understand how a typical Finnish housing company could modernise its energy system, reduce long-term costs and make better use of local solar production.
The Marttila pilot emerged through cooperation between two projects in Finland. StartSun found its case study through collaboration with Valonia and its TEMU project, which had already been examining how housing companies could benefit from energy communities.
Although the original aim had been to create a fully operational solar energy community, real-life implementation constraints led the Green Net Finland team to use Marttila as a practical pilot for testing frameworks, feasibility and decision-making.
“We needed a real case that would allow us to test what an energy community could look like in practice,” the Marttila story could be summed up.
Why this case matters:
Marttila shows how modelling can help housing companies turn a complex energy idea into a decision.
Main challenge:
The local grid, roof condition and financing slowed implementation.
Lesson for others:
Check the building, calculate the case and explain the benefits before expecting a decision.
It started from a real housing property
Marttila was a suitable place to explore the model because it reflected a common Finnish situation. The pilot site was a municipally owned rental housing company made up of terraced houses, with two buildings and six apartments. Built in the 1990s, the property represented the kind of housing stock that many municipalities and housing companies across Finland are trying to update.
The site also had a clear technical challenge. It needed to move away from oil heating, and the transition to an air-to-water heat pump increased electricity demand. Future needs, such as electric vehicle charging, also had to be taken into account.
This made the site a realistic test case for how local energy production could support a building’s changing energy use. The property manager was already thinking in long timeframes rather than short-term fixes, which made the case especially useful.
An energy community as a practical model
In Marttila, the energy community idea took shape within the Finnish model of a property-internal energy community. This is the most straightforward approach in Finland, because it uses the housing company’s existing grid connection and makes it possible to allocate solar electricity to both common building consumption and residents’ own use.
That made the concept practical rather than abstract. The pilot explored how solar production could be shared fairly between the housing company and tenants by using Finland’s official credit calculation model through Fingrid’s Datahub.
If the case had been approached only as a technical solar project, the discussion would have remained narrower. Looking at it as an energy community made it possible to ask broader questions about fairness, distribution of benefits, resident impact and long-term resilience.
The role of modelling quickly became central. Instead of relying on general enthusiasm, the pilot focused on concrete figures: investment costs, expected savings, payback time, risks and distribution of benefits.
Clear figures build confidence
One of the clearest lessons from Marttila is that energy communities become easier to understand when they are explained through real calculations. The modelling work helped turn a complicated idea into something concrete and discussable.
Board members and decision-makers need more than a general description. They need reliable information about costs, savings, maintenance, payback time, legal issues and potential risks.
The modelling also produced useful reality checks. For example, it showed that integrating a battery energy storage system would not be financially viable because of high maintenance costs. That helped avoid an unprofitable investment and redirected attention to a more sensible goal: maximising the self-consumption of solar energy.
In this way, modelling did not simply support the idea. It also sharpened it.
Questions came before decisions
In Marttila, the first discussions were focused. Because the property manager already understood the site’s technical characteristics, the main interest was in feasibility calculations, profitability of solar PV, fire safety and equipment placement.
The main doubts were practical. People wanted clarity on fire safety, insurance and whether the planned solar solution would make economic sense. These are the concerns that determine whether an energy community remains an interesting concept or becomes a credible project.
Trust matters greatly in this process. An energy community is not a short-term experiment but a long-term commitment, both financially and technically. Decision-makers need to feel that the data is reliable and the proposal is grounded in realistic assumptions.
In Finland, housing company decision-making is structured and democratic. The board usually prepares a proposal, and the final decision is made by stakeholders through a majority vote at the general meeting. In Marttila, the municipally owned nature of the property added another layer, because public stakeholders also had to be considered.
Technical barriers slowed progress
The Marttila pilot showed how decisive technical and infrastructural barriers can be.
One major challenge was the local electricity grid. Changes in the heating system and preparation for future loads meant that the distribution system operator had to reinforce the regional grid. This caused a delay of around one and a half years.
The roof created another obstacle. Because the existing 1990s roof was not structurally suitable for solar panels, a full renovation was needed before installation could move forward. Fire safety requirements also had to be mapped carefully, including the placement of the inverter and firefighter safety switches.
Financial questions were present as well. The housing company already had debt related to renovations and other necessary expenses, which meant that financing an energy community could have been difficult even if the technical side had been ready.
All this showed that the path from idea to implementation depends heavily on the overall condition of the property. Before additional investments are made, the sustainability basics of the building need to be in place.
Low awareness, strong relevance
Another lesson from Marttila is that the concept of energy communities is still not widely familiar in Finland. For many housing companies, boards and residents, the practical meaning remains unclear.
At the same time, Finnish legislation and technical systems already support one specific and practical form of energy community: shared solar energy within housing companies.
That means the challenge is not only legal or technological. It is also communicative. Energy communities need to be explained in a simple and practical way. When the idea feels too complex, people hesitate. When it is described through real examples, calculations and understandable benefits, it becomes easier to discuss.
Housing companies need clear guidelines, expert support, reliable decision-making tools, financial support and opportunities to learn from comparable pilots.
What Marttila teaches others
The most valuable lesson from Marttila is that an energy community should not be planned in isolation from the wider condition and future of the property. The building, its renovation needs and its long-term development path must be studied first.
Marttila also shows the value of open communication and steady cooperation. The case advanced through repeated discussions between the property manager and the Green Net Finland team. With every meeting, the shared understanding improved.
The idea has not yet fully moved from modelling to implementation. One remaining issue is funding. Many housing companies lack the financial capacity to move ahead alone, even when the concept is sound.
Still, the pilot has shown why this model matters. In the long term, energy communities can help residents by making energy costs more stable and predictable while improving local resilience.
If the Marttila story had to be captured in one sentence, it might be this: clear modelling, steady cooperation and practical communication can turn an abstract energy idea into a concrete and achievable plan.
Interested to learn more?
Join us on 22 September 2026 for the conference “From Concept to Community: Launching Solar Energy Communities“. This conference brings together local authorities, community initiatives, apartment associations, energy community leaders, developers, researchers, entrepreneurs and others interested in local renewable energy.
The conference will share practical experiences, success stories and challenges from developing solar energy communities, including technical, social and funding-related aspects, as well as cooperation models for turning ideas into action. Participants will also be introduced to the StartSun handbook and energy community feasibility calculator. The conference will be held in English and is co-funded by the European Union.