Heat pump (PAC, Pompe a chaleur): French types and terminology explained

How a heat pump works

A heat pump doesn't generate heat by burning fuel. Instead it extracts thermal energy from the outside air (or the ground) and moves it indoors. The process uses a refrigerant circuit, similar to a fridge working in reverse. Even when outside temperatures are low, there's enough thermal energy in the air to extract.

The efficiency of a heat pump is measured by its COP: coefficient de performance. A COP of 3 means that for every 1 kWh of electricity consumed, the system produces 3 kWh of usable heat. The actual COP varies depending on the outside temperature: higher in mild conditions, lower when it's very cold. This is why the Cote d'Azur climate suits heat pumps well. Even in January, outdoor temperatures here rarely drop low enough to significantly reduce performance.

PAC reversible

In France, most residential heat pumps sold are reversible: they can both heat in winter and cool in summer. When heating, the system extracts heat from outside and delivers it inside. When cooling, the cycle reverses and it operates like an air conditioner. You'll see the term "PAC reversible" used on quotes and product specifications.

Reversibility is the main reason these units have become so popular on the Cote d'Azur: one system handles both seasonal needs. For MaPrimeRenov' purposes, the grant applies to the heating function, not the cooling.

PAC air-air vs PAC air-eau

These two terms describe how the heat is delivered inside the property:

• PAC air-air: the system heats or cools air directly, distributed through indoor units (splits) mounted on walls or ceilings. This is the most common type in the south of France. It does not heat water for domestic hot water or radiators.
• PAC air-eau: the system heats water, which is then circulated through radiators, underfloor heating, or a hot water cylinder. More complex to install, particularly if the property has old or undersized radiators. Better suited to properties with existing wet heating systems.

Ground-source heat pumps (PAC geothermique) are a third type: they extract heat from the ground rather than the air, via buried pipes or boreholes. They are more expensive to install but can achieve higher COP values because ground temperatures are more stable than air temperatures. Less common in the region due to installation cost and the requirement for sufficient land or borehole depth.

What you'll see on a quote

A devis for a PAC installation will usually list the brand and model of the outdoor unit (groupe exterieur) and the indoor unit or units (groupes interieurs or splits). It will specify the capacity in kW and often the seasonal efficiency rating (SCOP for heating, SEER for cooling). These ratings are used in calculating MaPrimeRenov' grant amounts.

Related terms

• MaPrimeRenov': the main government grant for heat pump installations
• RGE certification: specifically QualiPAC for heat pump contractors
• Devis: the written quote you'll receive before any installation

Further reading

• Heat pumps on the Cote d'Azur
• Reversible heat pumps