Aerothermal energy is one of the fastest-growing renewable heating and cooling technologies in Europe and North America. If you’ve seen the term on an energy bill, a government subsidy list, or a home renovation forum, this guide breaks down exactly what it is, how it works, and why so many homeowners are switching to it.
What Is Aerothermal Energy?
PleaAerothermal energy is heat extracted from the ambient air and converted into usable energy for heating, cooling, and hot water. The technology that captures this energy is called an air source heat pump (ASHP). Unlike a traditional boiler that burns fuel to create heat, a heat pump moves existing heat from one place to another — even when outdoor temperatures are near freezing.
This makes aerothermal systems part of a broader family of renewable heat sources, alongside:
Aerothermal energy — heat extracted from the air (the most widely installed option, since it requires no drilling or nearby water source)se try a search with different keywords.
Geothermal energy — heat extracted from the ground
Hydrothermal energy — heat extracted from water sources
How Does an Air Source Heat Pump Work? (Step by Step)
A heat pump works by exploiting a basic principle of physics: when a refrigerant gas is compressed, it heats up; when it expands, it cools down. Here’s the cycle broken into stages:
Step 1: Heat absorption from outdoor air
A fan draws outside air across an outdoor evaporator coil. Inside the coil, a refrigerant with a very low boiling point absorbs heat from the air and evaporates into a gas — even when it’s cold outside, since the refrigerant boils at temperatures as low as -25°C.
Step 2: Compression
The refrigerant gas travels to a compressor, which is the heart of the system. Compressing the gas significantly raises its temperature and pressure, concentrating the low-grade heat collected from the air into high-grade, usable heat.
Step 3: Heat transfer (condensation)
The hot, high-pressure gas moves through a condenser, releasing its heat into your home’s water-based heating circuit (radiators, underfloor heating, or a hot water tank). As it releases heat, the refrigerant condenses back into a liquid.
Step 4: Expansion and pressure drop
The liquid refrigerant passes through an expansion valve, which drops its pressure and temperature dramatically, preparing it to absorb heat again.
Step 5: Cycle repeats
The cooled refrigerant returns to the outdoor evaporator, and the cycle starts over — continuously moving heat from outside to inside.
This is the same principle used by a refrigerator, just running in reverse: instead of pulling heat out of a box to keep food cold, the heat pump pulls heat out of the air to keep a house warm.