Installing a ground source heat pump

Ground source heat pumps use highly energy-efficient technology to heat homes and other buildings. But whether it's the right choice for you will depend on several factors, including how much garden space you have. 

Below, we explain what you need to consider before installing a ground source heat pump, including the difference between a horizontal and vertical ground array and how to find an approved installer.

For most households in the UK, an air source heat pump may be more appropriate. Find out the difference between the two in our introduction to heat pumps.

Or head to our guides to air source heat pump costs and savings and ground source heat pump costs and savings for more in-depth information.

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Should you buy a ground source heat pump?

Here are five key things you need to think about if you are considering installing a ground source heat pump:

1. The size of your home and garden

Ground source heat pumps are better for larger homes that use a lot of heat. You'll need enough outdoor space to install the ground array, including access for specialist digging machinery. Ask an installer to assess whether your home and garden are suitable.

2. Existing fuel and heating system

Energy bill savings will be greater if you're replacing an old or expensive heating system (such as LPG or direct electric heating) than if you're currently using mains gas. 

If you don't already have a wet central heating system - that is, one with radiators and/or underfloor heating fed by hot water pipes - you'll have to install the entire system from scratch, which will increase the upfront cost and be more disruptive.

3. Existing radiators

A ground source heat pump produces low-temperature heat, so is best connected to a system that's designed for this, such as underfloor heating.

If your existing radiators are small and you're used to having them scorching hot, they may not be able to heat your home as quickly, or to the temperature you are used to, with a heat pump. You may need to add more radiators, or replace them with larger radiators and/or underfloor heating, all of which will increase the total installation cost.

4. Water heating

If you are replacing a combi boiler and don't have a hot water tank, you'll need a suitable space to install a new hot water storage cylinder. Alternatively, if you install a heat-only heat pump, you'll need a separate method of water heating, such as an immersion heater.

5. Insulation

Before installing a ground source heat pump, check your home's energy efficiency. If appropriate, add loft and cavity wall insulation, or other energy-saving measures to ensure your heat pump runs as efficiently as possible.

If your home is not well insulated, you'll be paying more to generate heat that quickly leaks out of your home.

Find out more about how to insulate your home. 

Horizontal and vertical arrays: what's the difference?

The ground array (the network of pipes pumping the thermal transfer fluid underground) can be laid horizontally or vertically. The type of system you choose depends on the space you have available and the local geology.

Horizontal systems use lengths of pipe laid in shallow trenches around one to two metres deep. 

As a rule of thumb, you'll need 10m of trench with per kilowatt of the heat pump size. So, a 4kW heat pump will require 40m of trench with pipes buried in the ground for space heating. If you need it to supply hot water as well, the trench will need to be slightly longer.

The Ground Source Heat Pump Association estimates that a new-build three-bedroom house (around 120m²) would need two trenches of 30 to 40 metres long.

Horizontal ground arrays require more ground area than vertical arrays like boreholes, but they are cheaper to install because there is no need for specialist drilling equipment.

Vertical arrays bury the pipes in a deep borehole. Depending on the size of the system, the borehole could be up to 200 metres deep, although it is less than a metre in diameter. 

Whatever type of ground source heat pump you install, it's important that the system is correctly sized for your heating needs.

If your garden isn't suitable for a ground source heat pump, you could consider an air source heat pump instead.

Installing a ground source heat pump

Both types of installation - in trenches or boreholes - need access to your garden from the road for digging machinery to carry out the groundwork. 

For a borehole, although the area needed is quite small, you'll still need enough space for the specialist drilling rig.

The heat pump unit (containing the compressor and heat exchanger) will be installed inside your home. You'll generally need a space approximately the size of a fridge-freezer, although smaller versions - around the size of an under-counter fridge - are available for smaller homes.

You'll also need a large hot water cylinder - a similar size to the heat pump unit - and possibly a smaller buffer or header tank as well.

Ideally you'll have a plant room or utility room to contain all the components, along with the associated pipework and controls.

The installation of a ground source heat pump typically takes one to two days for a professional installer to complete.

Can I install a DIY ground source heat pump?

Installing a ground source heat pump is not a DIY job. Although you may be able to carry out some of the work yourself - such as digging the trenches for a ground loop - the sizing, design and installation should be done by a suitably qualified professional.

If you're ready to find out more, look for a Microgeneration Certification Scheme (MCS) certified installer.

Using an MCS certified installer ensures that the equipment meets good standards of performance and that installers are technically safe and competent.

Only MCS installers can apply for the Boiler Upgrade Scheme grant on your behalf, which can give you up to £7,500 towards the cost (in England and Wales only).

The MCS website also lists MCS-certified products, including ground source and air source heat pumps, that comply with specific standards for quality, reliability and performance.

Use our Which? Trusted Traders search tool below to find an accredited trader near you. All of our traders have been vetted so you can trust them to do a great job and all are MCS certified.

Do you need planning permission for a ground source heat pump?

The installation of a ground source heat pump is usually considered permitted development, so you don’t need planning permission. As ever, if you live in a listed building or a conservation area you should contact your council to check on local requirements.

Because the heat pump unit can be installed indoors, there is normally no visual change to the exterior of your home. 

Ground source heat pumps operate quietly and, as the unit is inside your home, there is no noise impact on neighbouring properties.

Heat pump energy labels

Heat pump energy labels give information about the energy efficiency of the heat pump with ratings from dark green (most efficient) to red (least efficient).

Since March 2016, all heat pumps must be sold with a product label, and the installer must produce a package label. 

If your heat pump supplies both space heating and hot water, then – like a gas combi boiler – the label will indicate how efficient the heat pump is for each function.

Heat pump energy labels also indicate how noisy they are, displaying the decibel level both inside and outside the home.

Ground source heat pump controls

Like any heating system, understanding how to operate it efficiently will help you make your home more comfortable and minimise your bills. Your installer should show you how the controls work, including how to set the temperature of both the heating and hot water, and how to programme your heating schedule. They should also supply you with an operating manual.  

Your heating controls should allow you to pre-program your system to switch on or off at different times. This is especially important to make the most of cheaper electricity on heat pump or time-of-use tariffs, as you may pay a much higher price for electricity at peak times compared with the off-peak rates.

Read more: an introduction to heat pumps

Looking to generate your own electricity? Head to our solar panels buying advice.