Air source heat pumps take heat from the outside air and use it to warm homes and buildings.
Unlike a boiler, they do not burn fuel to create heat. Instead, they move heat from one place to another, making them a cleaner and more energy-efficient way to heat spaces and water.
Although they use electricity, heat pumps can deliver far more heat than the energy they consume. Because of this, they play an important role in low-carbon heating.
In simple terms, an air source heat pump collects heat from the air, boosts that heat, and moves it indoors.
What Is an Air Source Heat Pump?
An air source heat pump is a heating system that moves heat rather than creating it.
A simple way to understand it is to think of a fridge—but in reverse.
- A fridge removes heat from inside and releases it outside
- A heat pump takes heat from outside and releases it inside
Even cold outdoor air contains usable heat, and the system is designed to capture it.
Most air source heat pump systems include:
- An outdoor unit with a fan and heat collector
- A compressor that raises temperature
- Pipes containing a special refrigerant fluid
- An indoor unit connected to radiators, underfloor heating, or hot water
- Controls that manage temperature and timing
Together, these parts move heat from outside into your home.
How Heat Is Collected and Used
The system works in a continuous cycle.
1. Heat Is Collected from the Air
The outdoor unit draws in air using a fan.
Even in cold weather, that air still contains heat. The system absorbs this heat into a special fluid called a refrigerant.
2. The Heat Is Boosted
The refrigerant then passes through a compressor.
As the compressor squeezes the fluid, its temperature rises sharply.
This is what turns low-grade outdoor heat into useful heating for your home.
3. Heat Moves Indoors
Once heated, the fluid travels to the indoor unit.
Here, it transfers heat into your home’s heating system.
4. Rooms and Water Warm Up
That heat then flows through:
- Radiators
- Underfloor heating
- Hot water cylinders
As a result, rooms warm up and hot water becomes available for taps and showers.
5. The Cycle Repeats
After releasing its heat, the fluid cools and returns outside.
It then collects more heat from the air, and the cycle begins again.
This process repeats continuously while heating is needed.
Main Parts of a Heat Pump
Outdoor Unit
The outdoor unit pulls in air and captures heat from it.
Compressor
The compressor raises the temperature of the collected heat.
Refrigerant Pipes
These pipes carry heat around the system.
Indoor Unit
The indoor unit transfers heat into radiators, underfloor heating, or hot water storage.
Control System
The controls manage when the system runs and what temperature it aims for.
From Air to Home
Heat moves from the outside air into the heat pump and then into your home.
Although the system uses electricity to run fans and compressors, it produces much more heat than the power it consumes.
For example, 1 unit of electricity can often deliver 3–4 units of heat.
Because of this, air source heat pumps can be highly efficient.
Why Air Source Heat Pumps Matter
Air source heat pumps can heat homes without:
- Burning gas or oil
- Producing carbon dioxide at the property
- Creating smoke or fumes
They also work throughout the year and pair especially well with renewable electricity such as solar or wind power.
As a result, they can help reduce both carbon emissions and long-term energy costs.
In Short
Air source heat pumps follow a simple cycle:
- Collect heat from the outside air
- Boost that heat using a compressor
- Move the heat indoors
- Warm rooms and water
By repeating this cycle, they provide clean, efficient heating for modern homes.