Air source heat pumps vs ground source heat pumps

When it comes to energy efficient heating systems, the two main types of heat pump are air source and ground source. But if you’re looking to switch, which one is more suitable to you? Let’s take a look at their similarities and differences.

• Ground source heat pumps cost much more to install than air source units, but they'll both qualify for a £7,500 government grant.

• Air source units are compact and quick to fit, whereas ground source systems require a large outdoors space.

• They'll both last for decades, but ground source systems are more consistently efficient in freezing winter weather.

Price

Both air source and ground source heat pumps require a hefty upfront investment. However, while air source heat pump installation can cost around £11,000, ground source heat pumps can cost anywhere between £11,500 and £49,000 depending on the size and complexity of the installation, making them significantly more expensive.

They do both qualify for the government’s Boiler Upgrade Scheme, which can help alleviate some of the initial cost with a £7,500 grant.

Size

The main unit of an air source heat pump sits outside your home and is usually between 1 and 1.5 metres tall and between 0.5 and 1 metres wide. That means it’s roughly the size of two wheelie bins standing side by side.

Ground source heat pumps are much bigger, but most of the system will be underground on your property, out of the way.

Longevity

If you take good care of your air source heat pump and provide regular maintenance and servicing, the unit can last between 20 and 25 years.

With ground source heat pumps, the interior mechanical unit can last a similar amount of time before needing to be replaced, but the underground loop and pipes can last much longer, somewhere in the range of 50 to 100 years.

Installation

Air source heat pump installation is relatively straightforward, taking a matter of days or possibly a full week.

Ground source heat pumps take quite a bit longer due to the complex and intensive work involved. The process of digging trenches and installing the underground loop can take weeks or months.

Efficiency

With air source heat pumps, for every unit of electricity you put in, you'll get three times as much heat back for a 300% efficiency rating. However, if temperatures drop below 0°C the unit has to work harder to extract heat from the air, and the efficiency can drop as low as 200%.

Ground source heat pumps on the other hand, maintain a consistent 400% efficiency rating all year round. This is due to the temperature remaining stable underground regardless of the season.

Suitability

Air source heat pumps are suitable for most types of properties. Some, like flats, can be tricky but not impossible.

Ground source heat pumps require a lot of space on the property so that trenches can be dug for the underground unit.

Having compared air source and ground source heat pumps, we hope the distinctions between the two are a little clearer. Overall, it seems that ground source heat pumps last longer and are more consistently efficient but cost exponentially more and aren’t suitable for every home type. If you’d like to learn more, consider our guide to the various different types of heat pumps.

Either heat pump system will be suitable for a well-insulated new build. The decision largely depends on how much you want to spend on the initial installation and how much space you have.

Water source heat pumps operate in a very similar way to ground source heat pumps, but they require having an accessible water source on your property to extract heat from.

Ground source heat pumps tend to offer higher efficiency and savings in the long term due to consistent underground temperatures. However, they do require a much bigger upfront investment than air source heat pumps.