SHOULD I INSTALL AN AIR SOURCE OR GROUND SOURCE HEAT PUMP?

Our renewables and sustainable energy expert explains the key differences between these two types of heat pump to help you choose the right one for your project

- DAVID HILTON

If you're looking at heat pumps in the UK, you'll likely be considering whether an air source heat pump or ground source heat pump will be best suited to your home. Air source heat pumps will eventually become standard in new-build homes, although both types of heat pump are already a mainstream consideration for self-builders or renovators looking to replace existing gas, oil or LPG heating systems.

At the heart of any type of heat pump is the vapour compression cycle (refrigeration), that uses a refrigerant liquid to absorb heat from the environment and transfer it as useful heat to the home. But how does each type of heat pump differ and when might one be more suitable than the other?

Here, I explain the key differences in order that you can make an informed decision when specifying a heat pump for your home property.

THE KEY DIFFERENCES BETWEEN THE TWO

The main difference in how an air source heat pump (ASHP) works compared to a ground source heat pump (GSHP) is where each unit draws its heat from. The clue is in the name, with one using air and the other using the ground.

An air source heat pump draws heat from the air around the heat pump unit. In terms of the air source heat pump positioning, the unit is usually placed outdoors and a fan blows air across a finned heat exchanger containing very cold refrigerant that absorbs heat from the air passing over it.

As the refrigerant absorbs the heat, it 'boils' and becomes a gas. This gas then passes into a compressor where it is compressed and rises in temperature due to the pressure. The hot gas then passes through another heat exchanger where the heat from the hot gas is transferred into the central heating water in the home.