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What's the Best Option for you? Air Source Heat Pumps vs Ground Source Heat Pumps.

So, you’ve decided you want to have a heat pump installed, but you’re now trying to decide between air source and ground source. Have a read through our handy guide to help you choose.

Air Source Heat Pumps

Air source heat pumps are the most cost effective and quickest type of heat pump to install. They work by extracting energy from the outside air which is then transferred to the refrigerant within the heat pump and compressed into a gas. This process raises the temperature of the gas which in turn is used to provide heating and hot water into homes and buildings.

Air source heat pumps consist of an outdoor unit which look similar to an external air conditioning unit and make a similar level of noise to a traditional gas boiler. This outdoor unit is controlled by a small controller which is usually located within a utility or plant room, alongside a hot water cylinder.

As air source heat pumps use the energy from outside air, they are most effective when the temperature is warm but can work down to temperatures as low as -25 degrees. They run on electricity and can be up to 400% efficient – this means that for every 1kW of electricity the heat pump consumes, it can produce up to 4kW of heating capacity.

Most air source heat pumps do not require planning permission as they usually fall under ‘permitted developments’ but if your building is listed or you live in a conservation area, then you should check with your local planning authority.

Air source heat pumps generally require little maintenance; we recommend an annual health check to keep your heat pump running as efficiently as possible and to carry out any preventative maintenance, ensuring your heat pump remains in good, working condition throughout the year.

Ground Source Heat Pumps

Ground source heat pumps work in a similar way to air source heat pumps, except instead of extracting energy from the outside air, it uses the energy from the ground. It is able to do this because when you install a ground source heat pump, you will need to install ‘ground arrays’ or ‘boreholes’ which are large pipes installed in the earth outside of the property. It is for this reason, that ground source heat pumps cost so much more than air source heat pumps to install.

Ground arrays are more cost effective to install than boreholes; they are run horizontally within the ground and therefore you need a significant amount of land to house them. Boreholes are much more expensive but are dug vertically, which means only minimal land is required.

Ground source heat pumps will require a little more space inside than an air source heat pump needs, the units are usually located within a utility or plant room but could also be stored in a kitchen cupboard or airing cupboard and they make a similar noise to a dishwasher. As with an air source heat pumps, there will also be a hot water cylinder inside.

The ground provides a more stable temperature than the air, particularly in the colder months and for that reason ground source heat pumps are more efficient than air source heat pumps which could result in lower running costs. That being said, you are unlikely to recoup the difference in installation costs through the savings in running costs between ground source and air source heat pumps.

Similarly to air source heat pumps, ground source heat pumps do not usually require planning permission unless your property is subject to any special requirements or your installation is particularly large in size. The maintenance requirements are also minimal, the same annual service is recommended for ground source heat pumps.

In summary, the choice on whether a ground source or air source heat pump is best, is project dependent. We’ve put together this quick crib sheet to help you:

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