AIR SOURCE HEAT PUMPicon-128px-air-source


An air source heat pump (ASHP) is a renewable energy system which transfers heat from the outside to inside a building, or vice versa. Under the principles of vapor compression refrigeration, an ASHP uses a refrigerant system involving a compressor and a condenser to absorb heat in one place and release it at another. They can be used as a space heater or cooler, and are sometimes called “reverse-cycle air conditioners”.

The technology is similar to a refrigerator, freezer or air conditioning unit; just as the pipes on the back of a refrigerator become warm as the interior cools, so an ASHP warms the inside of a building whilst cooling the outside air. A high efficiency heat pump can provide up to four times as much heat as an electric heater using the same energy.

The main components of an air source heat pump are:

• An outdoor heat exchanger coil, which extracts heat from ambient air

• An indoor heat exchanger coil, which transfers the heat into hot air ducts, an indoor heating system such as 

water-filled radiators or underfloor circuits and/or a domestic hot water tank

Suitable for a wide range of domestic, corporate and commercial premises keen to generate sustainable energy, air source heat pumps can be fitted externally to buildings for heating and cooling purposes. Heat pumps are ideal for commercial heating solutions. Green energy technologies are extremely reliable and require little maintenance.

Like ground source heat pumps, they do have some impact on the environment and are not entirely carbon neutral as they require electricity to run. But, as they produce approximately 3 times more energy than they consume, the carbon emission savings of heat pumps are significant.


Heating and cooling is accomplished by pumping a refrigerant through the heat pump’s indoor and outdoor coils. Like in a refrigerator, a compressor, condenser, expansion valve and evaporator are used to change states of the refrigerant between colder liquid and hotter gas states.

When the liquid refrigerant at a low temperature and low pressure passes through the outdoor heat exchanger coils, ambient heat causes the liquid to boil, which changes it to a gas. The gas is then compressed using an electric pump which increases its temperature.

Inside the building, the gas passes through a pressure valve into heat exchanger coils. There, the hot refrigerant gas condenses back to a liquid and transfers the stored latent heat to the indoor air, water heating or hot water system. The indoor air or heating water is pumped across the heat exchanger by an electric pump or fan.

The cool liquid refrigerant then re-enters the outdoor heat exchanger coils to begin a new cycle.

Air source heat pumps make use of free sustainable energy from the air outside to power radiators and underfloor heating systems. The technology can also operate in a cooling mode where the cold refrigerant is moved through the indoor coils to cool the room air.

Air source heat pump efficiency is measured by their co-efficient of performance (COP), which is the ratio of the heat delivered to the electrical energy consumed to generate it. If the ratio is higher, the unit is more efficient. The COP of air source heat pumps varies depending on the installation, but is expected to be around 3.4, which means that, for every kWh of electricity it consumes to run, it will produce the equivalent of 3.4kWh of heat, reducing your heating energy consumption considerably.


Environmental Energies supplies and installs air to air and air to water NIBE heat pumps to lower your carbon footprint and save you money on your energy bills.

Our industrial specification heat pump systems provide substantial amounts of heating and hot water, which can be distributed by warm air distribution, under floor heating or radiators.

We provide only the highest quality NIBE air source heat pumps, and our products are eligible for the government’s Renewable Heat Incentive (RHI) domestic and non-domestic scheme.

icon-64px-case-studiesAIR SOURCE HEAT PUMP CASE STUDY

Discover how we’ve used air source heat pumps to reduce costs, carbon footprint and taxes.