The Ins and Outs of Ground Source Heat Pumps

Ground source heat pumps are becoming more mainstream than ever, consistently being thrust into the spotlight as a low-carbon alternative to gas boilers. But is a ground source heat pump right for you and your home? Here we give the 101 on them so you can make an informed purchase decision for your property.

What is a Ground Source Heat Pump?

Ground source heat pumps use a series of buried pipes to extract the energy soaked up into the ground from the sun. The pump within then amplifies that energy into heat for a home. There are two main elements to the system:
- A ground array, which is either a horizontal grid of pipes about 1.2m below ground level or two or three vertical boreholes as deep as 70m. The ground array from which to extract the sun’s warming energy on the ground by will determined by the overall size of the heat pump and the soil conditions within which it resides
- The heat pump itself. This is installed in the house as a unit and can be the size of a kitchen cupboard. Most pumps are fitted in a dedicated plant room for easy access but they can also be installed into other rooms as required. Usually it’s easiest for the pump to be installed close to an external wall near to the ground array, for access.
Ground source heat pumps do need electricity to work but they use it in a very efficient way and so significantly reduce heating running costs compared to traditional heating solutions. They can also be combined with other energy sources such as solar panels.

How do Ground Source Heat Pumps work?

The heat pumps use compression and expansion technology to extract and amplify the heat absorbed from the ground array (which is provided by solar energy and stored in the earth).
As a general rule, an area of 50m² is need for 1kW of heat output. This means that providing soil conditions are optimum (damp and clay), an 8kW heat pump will need 400m² of surface area (underground).
Of course, this does mean that ground source heat pumps aren’t suitable for everyone as they may not have sufficient land or have a property situated in suitable soil conditions. A heat pump installer will investigate into all of this before any action is taken.

What are the different types of Ground Source Heat Pumps?

There are three main types of heat pump currently available:
- Horizontal ground array – the most common type, with an array of either straight or coiled pipes
- Borehole ground array – boreholes drilled into the ground and connected across their tops
- Water source – making use of bodies of water such as lakes, rivers, ponds and streams. The pipes are installed via pond mats submerged into the water.

What are the benefits of Ground Source Heat Pumps compared to more traditional heating methods?

Ground source heat pumps are a low-carbon heating solution so is considered an environmentally-friendly option compared to more conventional methods. If homeowners opt for a renewable energy-only electricity supplier than they are able to reduce their CO2 emissions for the property to almost zero! Incorporating the electricity used to power the energy pump with a renewable solution such as solar panels can lower this even further.
The running costs of ground source heat pumps are around 45% lower than gas boilers; which also ranks them significantly less costly than other renewables, such as air source heat pumps.
Generally speaking, once installed and up and running, a ground source heat pump is considered as reliable as a gas boiler – but its life expectancy will be around double.
Ground source heat pumps are favoured by local authorities and government schemes as a result of their sustainability credentials. This means that there are often grants available to offset the cost of their installation, such as the government’s Boiler Upgrade Scheme.

What are the disadvantages of Ground Source Heat Pumps?

Of course, nothing is perfect. Ground source heat pumps do too have some disadvantages for homeowners.
Even when partially funded by a government or local authority grant, the high capital cost of installation for heat pumps is prohibitive for many. What’s more, the homeowner will need to have plenty of land for the installation and must consider significant disruption to the garden (especially when a horizontal ground array is being built).
Homeowners must too factor in the cost of upgrading their home’s insulation. Radiators should be replaced with low-flow versions or underfloor heating as the hefty heating systems installed in most homes as standard will no longer be required.

How much does a Ground Source Heat Pump cost?

There’s no one-size-fits-all for heat pumps, but there are some ballpark figures that can be considered.
A basic ground source heat pump costs between £2,000 - £15,000, dependent on its size and brand. This is about four times more expensive than a gas combi boiler and twice that of an air source heat pump. The quality of the heat pump equipment is broadly reflected in the cost; with those at the high end often allowing for on-board software to control and monitor its operations.
The installation of a ground source heat pump, including the purchase of the unit can usually be expected to cost between £15,000 - £25,000. This figure is impacted by the complexity of the installation, the type of installation and the size of the pump – larger properties will need larger pumps.

Where can I seek advice on Ground Source Heat Pumps?

Renovation firms and specialist contractors will be able to give advice on the suitability of a ground source heat pump as well as a cost estimate; but should really only do so upon a property visit to scope out the job. Refresh Renovations has worked with the installation of a variety of such pumps for homeowners internationally, so give us a call if you’d like to discuss more about what one may mean for you and your energy efficiency!
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