Published on · By the Faster-EV team
How it works
An air-to-water heat pump extracts heat from the outdoor air to heat the water in your heating circuit: radiators or underfloor heating. Depending on the model, it also produces domestic hot water and can cool the home in summer through the underfloor system or fan coil units.
Match the temperature to your heat emitters
Your heat emitters determine the water temperature needed. Underfloor heating works with water at about 35 °C, recent radiators at around 45 to 55 °C, and old cast-iron radiators at up to 65 °C or more. The lower the required temperature, the better the efficiency: for old radiators, choose a medium- or high-temperature model.
Monobloc or split
In a monobloc heat pump, the whole refrigerant circuit is inside the outdoor unit and sealed at the factory: only water pipes enter the home. Installation requires no work on the refrigerant, but the outdoor pipework must be protected against frost.
A split heat pump separates an outdoor unit and an indoor module connected by refrigerant lines: it must be connected and commissioned by a company holding a refrigerant handling certificate.
Size it with a heat loss calculation
Capacity is calculated from the home’s heat losses at your region’s design outdoor temperature. An oversized heat pump runs in short cycles; an undersized one relies more on its electric backup heater in very cold weather. Ask your installer for a heat loss calculation rather than reusing the capacity of your old boiler, which is often oversized.
Hot water and electrical supply
For domestic hot water, choose between a model with a built-in tank and a wall-mounted module with a separate tank; a 150 to 200 litre tank often suits a household of three to four people. Also check your electrical supply: some models come in single-phase and three-phase versions, and the installation must be able to handle the unit and any backup heater.
Before you order
If you are counting on an energy renovation grant, check its conditions before buying: French public schemes (MaPrimeRénov’, energy savings certificates…) require, among other things, a company with RGE certification. In every case, have your installer confirm the model, capacity and accessories.