Citizens investments financed the combination of photovoltaic and solar thermal power supplies in a participatory housing project in Voiron.
The co-owners of the housing project are very committed to ecology and have chosen to build an efficient shared habitat with eco-materials. They wish to pursue their energy transition approach by implementing renewable energies by using the roof to install both photovoltaic and thermal solar panels. Several co-owners involved in the project are retired people with low incomes and had already mobilized their entire debt capacity with banks to finance the construction of their houses.

Buxia Energies (BE), a citizen energy company, was able to make a third-party investment in order to pay for the solar thermal and photovoltaic energy installations in accordance with their statutory purpose. In line with the vision proposed by the NegaWatt association to reduce energy consumption in the same time to replace production with more ecological energy sources, they seek to create projects that make sense for the territory and its inhabitants .
BE pays a rent to exploit the photovoltaic roof of the participatory housing estate.
BE has invested in solar thermal panels and hot water tanks. And the real estate civil company that brings together the co-owners rent the use of these installations for 10 years. The rent is based on the expected gas savings thanks to solar thermal installation. Thus, the installation does not present any extra cost for the inhabitants compared to a gas installation but works with 50% renewable energy .

Resources needed

• BE invested 15k€ for thermal installation and received a 9k€ AURA region's subsidy
• BE’s management is voluntary
• Legal advice requested to approve the contractual model
• Local manufacturer’s system and installer
• PV system cost is 20k€ reimbursed through electricity sale by feed-in tariff

Evidence of success

• High degree of customer satisfaction both in terms of the quality of the installation and in gaining temperature comfort
• Control of energy expenses for the co-owners in accordance with the forecasts
• 2019-2020 result : + 50% gas saving for 5 households
• High potential development in thermal sector for energy communities (66% of the building's energy needs are heat requirements)
• 3 new projects in development in 2021 at regional level

Difficulties encountered

• This project would not have been possible without the third party citizen investment
• Direct use of production with 24/7 operation
• Design of a new economic and contractual framework
• Rentability only possible with the subsidy of the Region
• Decision-making in co-ownership are difficult

Potential for learning or transfer

This project is very replicable with co-ownerships that would request it and that would be at the limit of their debt capacity. The contractual framework is now consolidated and replicable for other energy communities.
Other targets could be approached (small tertiary sector businesses with heating needs, existing social landlords' buildings, etc.) once the contractual model is consolidated.
Local energy communities are spreading around Europe. They represent a high potential to bypass the barrier of bank financing for RES systems.
This economic model can be transferable to other RES provided that their global cost (investment and functioning) is lower than fossil fuels.
Thermal systems are less often installed and operated by energy communities because the economic model appears to be riskier. However, heating needs are in the majority in the building sector, and we need to support the growing expertise of energy communities in this area.

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Main institution
Buxia Energies SAS
Rhône-Alpes, France
Start Date
November 2017
End Date


noemie zambeaux Please login to contact the author.