How does a heat pump work? The clear 2026 guide

How does a heat pump work, and why does it consume so little compared with conventional heating? The principle is both simple and a little counter-intuitive: rather than producing heat by burning an energy source, a heat pump simply moves heat already present in the environment. Here is how it works, explained without jargon.

The principle: moving heat, not producing it

An aerothermal heat pump captures the free heat present in outdoor air, even when it is cold, and transfers it inside your home. It is the same principle as a refrigerator, but reversed.

A refrigerant fluid circulates in a loop and goes through four stages: it captures heat from the air, it is compressed (which raises its temperature), it releases this heat to your home, then expands to start the cycle again. Only the compressor consumes electricity: this is why a heat pump returns several times more energy than it consumes.

Air-to-air or air-to-water: two families

There are mainly two types of aerothermal heat pump:

• The air-to-air heat pump: it distributes heat directly via indoor units (blown air). It can also cool in summer.
• The air-to-water heat pump: it heats the water of a central heating circuit (radiators, underfloor heating) and can produce domestic hot water.

The choice depends on your existing installation. The air-to-water heat pump is the one that most naturally replaces an old boiler, and it is the one that qualifies for the main renovation subsidies.

COP and SCOP: how to read performance

Two indicators measure the efficiency of a heat pump:

• The COP (coefficient of performance) indicates the ratio between the energy returned and the electricity consumed, at a given temperature (often +7 °C). A COP of 4 means 4 kWh of heat for 1 kWh of electricity.
• The SCOP (seasonal COP) measures this efficiency over the whole heating season. It is more representative of reality, as it takes temperature variations into account.

In cold regions, it is advised to rely on the SCOP rather than the nominal COP. A SCOP above 3.5 is a good target in an average climate zone.

MaPrimeRénov’ subsidies in 2026

Installing an air-to-water heat pump qualifies for subsidies, foremost among them MaPrimeRénov’, whose amount depends on your income. Since the reform that came into force in January 2026, the appliance must reach a performance threshold: for an air-to-water heat pump replacing fossil heating, the ETAS (seasonal energy efficiency) must be greater than or equal to 126%, which corresponds to a SCOP of about 3.15.

According to 2026 public sources, MaPrimeRénov’ by gesture funds the air-to-water heat pump in the range of 3,000 to 5,000 euros depending on the profile, and the combination with CEE can exceed 9,000 euros for the most modest households in certain configurations. These amounts and the eligibility conditions change: check your situation before committing.

Choosing and installing your heat pump wisely

Beyond the advertised performance, the quality of the installation is decisive: proper sizing and a qualified RGE installer (essential for the subsidies) make all the difference to the real bill.

To compare models and brands, see our selection of the best heat pump. And if you are looking to reduce your energy bill overall, our guide to the best solar panel installer explores a complementary solution, often paired with a heat pump.