23-Degree Challenge – Passivhaus Comfort in the Pyrenees with 100% Renewable Energy

In Aratorés, a village in the Aragonese Pyrenees, a unique installation has been carried out with a singular challenge: to maintain a 180 m² home at a constant temperature of 23 °C for all 8,760 hours of the year, entirely energy self-sufficient. Despite operating in a demanding climate, which required nearly 7,000 kWh of heat and 2,300 kWh of cooling during its first year, the Ecoforest heat pump, combined with a photovoltaic system, has been able to create a comfortable environment with zero annual electricity costs.

To achieve this, a ground-source ecoGEO⁺ 1-9  heat pump with HTR technology was installed, capable of providing heating, cooling, and domestic hot water (DHW). The system is powered via a 100-metre-deep vertical borehole, allowing the home to harness underground energy even under the extreme weather conditions of the Pyrenees. Both heating and cooling are distributed via underfloor heating implemented on each level of the house.

A Passivhaus Home

The home holds Passivhaus certification, guaranteeing a highly efficient thermal envelope and minimal energy demand.

EThe system achieves an SPF of 4.58, exceeding a value of 5 during September and October—a remarkable result given the low local temperatures, demonstrating the system’s high efficiency throughout the year. Additionally, the ecoGEO⁺ Compact 1-9 includes a 165-litre DHW tank, meeting the home’s daily hot water needs while minimising the space required for the plant room. The installation also incorporates a 10 kW photovoltaic system, allowing the home to operate completely independently from the grid.

Full Control with Zero Energy Costs

The installation also features intelligent management of photovoltaic surplus, maximising solar production and storing or redirecting it according to thermal requirements. The standard Ecoforest energy manager, connected in this case to a 500-litre buffer tank acting as a thermal battery, allows the system to raise the set temperature of the buffer when excess photovoltaic energy is available, improving efficiency.

Through the official Ecoforest app, the user can monitor key parameters in real time—such as temperature, production, and efficiency—understanding the system’s performance in a clear and intuitive way.

This standard hybrid system, combined with a battery, results in total home consumption of 7,280 kWh over a year being split as follows:

• 64% from direct consumption
• 23% supplied by the battery
• Only 13% from the grid

As a result, the house imports just 860 kWh annually while exporting 10,900 kWh. Thanks to this energy surplus, all electricity bills have been zero, reducing the energy cost of a second home by 90%.

Comfort and 100% Savings

Thanks to this comprehensive solution, the thermal comfort of this home—which would otherwise cost approximately €3,700 per year—is now achieved with maximum energy savings. The project demonstrates that achieving a net-zero model in demanding climates is not only possible but also highly efficient.