You are here: Home | Fuel options | Ground source pumps

Ground source heat pumps

Ground source heat pumps use the earth's natural energy to provide space and water heating.

Just two metres below ground the earth is warm, being around 18°C. This heat can be pumped out of the ground and transferred via pipework. A heat pump unit, sited internally or externally, then compresses, and hence further warms, the heat. This relatively low grade heat is released into the home typically through an underfloor heating system. It can also be used for water heating.

Installations costs/payback

The capital cost is high and they are costly to install. A typical installation would cost around £13,500*, therefore you can be looking at more than two times the cost of a solar and LPG system.
They work best with underfloor heating systems, which will be costly (especially for retrofit applications), and low temperature radiators.
Installations in older buildings can be quite costly because of the insulation required. Many older buildings can never be made suitably efficient to use an underfloor heating system or low temperature radiators.

Running costs

They are very energy efficient – for each kilowatt of electricity used to run the heat pump, three to four kilowatts of heat are delivered.
The running costs are relatively low so you can benefit from reduced fuel bills.
Because energy comes out of the ground, it’s under the property owner’s control and there won’t be any fuel increases (excluding electricity, which is subject to price fluctuations).
Typical running costs would be £400 per annum (based on Economy 10 tariff).^*

Carbon emissions / the environment

Ground source heat pumps produce less carbon emissions than conventional heating systems.

Features and benefits

They are safe and reliable.
There is no flue to install.
The heat pump can be installed outdoors – for example in a garage or outbuilding.
There is no fuel to store.
Ground source heat pumps have been used widely in other parts of the world, including North America and Europe, for many years.

Potential drawbacks

For a horizontal system you will need space to lay the pipe system down in trenches and for a 3 bed house that means 2 x 50m long trenches. If you don’t have room to lay the pipes horizontally, you can drill deep and lay
them vertically. However, drilling down 30 to 150m is no small job and you can hit difficult or unsuitable geology.**
A typical heat pump is about the same size as a large fridge, so not every property will have the space required.
They require an electricity supply to pump the heat. Three phase electricity may be required.
Ground source heat pumps are efficient at producing low-grade heat which means they are ideal for underfloor heating. If asked to raise the temperature of water above 35° C, ground source heat pumps become much less efficient and there is the risk of legionella if high water temperature (at least 65° C) is not achieved. It is therefore standard practice to put in an additional water heating system for sanitary water. LPG is a very effective fuel source of this system, and can also satisfy your cooking requirement and provide feature fires.

Sources