A collective heating system in Saint-Nazaire to reduce costs and environmental impact

Saint-Nazaire is committing to an ambitious energy transition with the launch of an innovative collective heating network, named Ester, which promises to revolutionize the way heat is distributed in urban and collective settings. This modern facility, the result of a partnership between the City of Saint-Nazaire, Saint-Nazaire Agglo, and major players such as Dalkia, a subsidiary of the EDF group, aims to provide a sustainable, cost-effective, and environmentally friendly solution for nearly 16,400 homes. Thanks to a system primarily based on renewable energy (ENR), this project combines economic performance and ecological responsibility while ensuring price stability for 30 years. New standards are thus being established to reduce dependence on fossil fuels while controlling costs related to collective heating.

A collective heating network in Saint-Nazaire: operation and economic advantages

The collective heating in Saint-Nazaire is resolutely looking to the future with the establishment of the Ester network. Unlike individual heating, which often relies on equipment that emits gas or oil, this centralized system delivers heat through a network of underground pipes. This 37-kilometer network connects the city of Saint-Nazaire to neighboring municipalities such as Donges and Montoir-de-Bretagne, thus promoting an efficient energy mesh. The principle is based on centralized hot water production mainly powered by renewable energy, which is then distributed to thousands of collective housing, public establishments, and businesses.

Here are the main advantages of this system:

• Reduced and controlled cost: The service guarantees a price approximately 30% cheaper than traditional gas, with stable price guarantees over the 30 years of the public service delegation.
• Ease of connection: Collective housing will not require heavy modifications. The individual boiler is replaced by a simple connection to the network.
• Enhanced energy performance: The network operates based on several combined renewable sources.
• Reduction of costs for households: This collective model perfectly fits into a social ecology logic, supported by the City of Saint-Nazaire, to alleviate the energy bills of residents.

Beyond pricing, the network meets reliability requirements thanks to recognized partners such as Enedis for electricity distribution, Veolia for fluid management, and RTE for energy network performance. The commitment of ENGIE, E.ON, and Suez in the local energy transition also contributes to strengthening this collective dynamic.

Characteristics	Details
Network length	37 kilometers
Number of serviced homes	16,400 (including 4,000 social housing units)
Share of renewable energies	90%
Estimated CO2 reduction	20,000 tons per year
Total investment	85 million euros

These elements were presented during the official signing of the contract by David Samzun, President of Saint-Nazaire Agglo and Mayor of the city, Pierre de Montlivault, Regional Director of Dalkia, and Xavier Perrin, President of Silène habitat, demonstrating a strong commitment from local stakeholders.

Renewable energies at the heart of the Ester network for a successful ecological transition

The main ambition of the Ester network is to achieve a share of renewable energy of 90%, an objective that places Saint-Nazaire among the pioneering cities in sustainable collective heating. The system relies on several local and environmentally friendly energy sources.

The wood sector: a renewable and local fuel

The network uses a wood boiler located in Montoir-de-Bretagne. It will operate with forest chips, wood from hedge maintenance, or packaging wood. This wood is sourced through rigorously selected local supply chains to ensure both security of supply and minimization of transport.

This high-tech boiler will allow for the valorization of a natural residue and significantly reduce greenhouse gas emissions. The choice of local wood also promotes the circular economy by maintaining jobs and local activities around forestry and the processing of green waste.

Energy recovery: deploying high-performance heat pumps

A next-generation heat pump will be installed near the Écossiernes wastewater treatment plant. This installation will recover the heat contained in wastewater, a thermal resource that is typically wasted. The use of this recovered energy, which does not involve direct consumption of fuel or gas, will quickly improve the overall efficiency of the network and reduce the energy bills of users.

Collaboration with local industries to valorize waste heat

The project also includes a partnership with several industries located in the area, which will agree to provide the heat generated from their manufacturing processes. These industries can also be connected to the network, creating an integrated energy loop. This mechanism further strengthens the local economy and the ecological relevance of the Ester network by reducing energy waste.

• Support from public authorities through subsidies from the Ademe.
• Commitment from local businesses and the public sector.
• Involvement of industrial players for a decarbonized economy.
• Use of proven renewable energies, securing both supply and performance.

Energy source	Advantages	Environmental impact
Local wood (forest chips)	Renewable, local valorization	Significant CO2 reduction
Wastewater heat pump	Energy recovery, efficient	Limited electricity consumption, high performance
Industrial waste heat	Resource optimization	Reduction of energy losses

The key stages of construction and deployment of the network

After the official signing of the public service delegation on June 19, the construction work will soon begin. The preparations mainly consist of burying the hot water pipes around the city and in the surrounding municipalities. This phase is crucial to ensure the efficiency and longevity of the network. Dalkia is responsible for the design, implementation, and operation for the next 30 years, ensuring recognized expertise and rigorous monitoring.

Here is the planned schedule:

• 2025: Start of work on the installation of underground pipes.
• End of 2026: Commissioning of the first connections, particularly in the social housing units of Silène.
• 2027: Complete installation of the wood boiler in Montoir-de-Bretagne.
• 2030: Goal of extending to 16,400 homes and maximum integration of renewable energies.

The programming of these phases has been designed to minimize inconveniences to residents, with quick interventions and protocols that respect the environment. The City of Saint-Nazaire and Saint-Nazaire Agglo closely monitor progress and involve the public through consultations and regular information.

Year	Key step	Description
2025	Start of work	Installation of pipes and foundations of the network
2026	First connections	Connection of collective housing Silène habitat
2027	Wood boiler operational	Complete commissioning of the main renewable energy source
2030	Extension and stabilization	Connection of more than 16,000 homes, energy optimization

This network brings a new dimension to collective heating, with a direct link between technological innovation and respect for the environment as well as strong local involvement.

Environmental impact and return on investment: a winning project for Saint-Nazaire

The Ester network stands out not only for its technical performance but also for its tangible impact in terms of carbon emission reduction. The goal is to avoid emitting more than 20,000 tons of CO2 every year, which corresponds to removing the equivalent of 10,000 thermal vehicles from circulation. This significant reduction contributes to the strong commitment of the City of Saint-Nazaire, associated with EDF through Dalkia, to move towards a cleaner and more resilient territory in the face of climate challenges.

In the long term, this collective system also ensures a return on investment by:

• A notable reduction in energy costs for subscribers.
• Better control of charges for social landlords and the community.
• The creation of jobs in local production and network management sectors.
• An increase in the asset value of connected homes.

The success of the project is also linked to the mobilization of specialized actors such as Suez and ENGIE, who bring their expertise in sustainable management of energy fluids and network optimization. The role of RTE in the management of electrical infrastructures is also crucial to ensure the balance and quality of service.

Indicator	Expected benefit
CO2 emissions avoided	20,000 tons per year
Reduction in energy bills	-30% on average
Guaranteed price duration	30 years
Connected homes	16,400

All these benefits encourage us to consider collective heating as a future solution for other French municipalities, especially in the current context where financial aid focuses on projects using renewable energies.

Practical advice for residents and managers on collective heating in Saint-Nazaire

For residents affected by this new system, it is important to understand that connecting to the Ester network does not require any technical intervention in their homes. The transition from an individual gas boiler to this collective system translates to a clean installation without invasive work. The costs related to heating will be directly billed to subscribers by Dalkia, with expected transparency and price stability.

Some recommendations for better managing your consumption and optimizing your comfort:

• Do not overheat rooms: a temperature set between 19 and 20°C is ideal.
• Properly insulate your home: heat loss should be minimized to maximize savings.
• Avoid repeated heating interruptions to limit overconsumption due to restarting.
• Take advantage of the maintenance service offered by Dalkia to keep the system efficient.

On their side, property managers must follow the annual maintenance schedule to ensure the safety and performance of the network over time. The rapid troubleshooting service is an essential added value, as it guarantees responsiveness in case of a breakdown, thus avoiding inconvenience for end users.

Advice	Positive impact
Optimal temperature setting	Reduction in energy consumption and better comfort
Effective thermal insulation	Limitation of heat loss, long-term savings
Regular maintenance	Safety and maintenance of performance
Monitoring of consumption	Quick adaptation to actual usage

For more details on how collective heating systems work and the assistance available, refer to this comprehensive guide here or the local information provided by the City of Saint-Nazaire.