- a long loop of pipe, filled with water and anti-freeze, is buried in the earth. Depending on available space it can be in a trench at least 1.5m deep or down a borehole
- the liquid in the pipe (or ground loop) absorbs heat from the ground which is a fairly stable 8 – 12 degrees C all year round
- as it passes through an electrically powered heat pump, the absorbed heat is extracted, and the liquid goes back into the underground loop
- using mains electricity, the heat pump boosts the heat from the ground to the level needed by the heating system, heating water in a buffer tank
- the heating system is fed from the buffer tank.
- reduce your carbon footprint
- reduce energy bills
- heat your home and water
- some financial return
Heat pumps aren’t suitable for every home. Heat pumps are designed to heat the water needed to heat your home to a lower temperature than traditional boilers. As a result, the ideal place for them is an extremely well insulated house with underfloor heating, as this provides a greater surface area than a traditional radiator. You can use a heat pump with radiators, but to get the same level of heat you will need larger radiators. Many older buildings are not energy efficient enough to use underfloor heating or low temperature radiators. Heat pumps can be cost effective in places where there is no mains gas supply. Heat pumps can replace gas or electricity heating.
The geology of the ground around your property is important in determining whether a ground source heat pump is suitable. For example, sandy soil drains fast and does not hold heat well. Heat pumps will not perform well in an area with this type of soil (although a more expensive borehole might work here).
You also need space outside to dig trenches, or sink deep boreholes, for the ground loop. As a rule of thumb, you’ll need twice the area of the property for the ground arrays. And you need suitable access for the drilling machinery if you are having boreholes.
The performance of a heat pump is rated as a seasonal performance factor (SPF). It is the total useful heat generated from the heat pump in a year divided by the annual electricity consumption. For example, an SPF of 3 indicates that the system will give an average three units of heat energy for each one unit of electricity used.
To be considered ‘renewable’ (under EU legislation) heat pumps must have a SPF of at least 2.5, and this is the minimum performance that is eligible for the Domestic Renewable Heat Incentive.
All heat pumps should be serviced every few years.
Heat pumps are expected to last for over 20 years.
Ground source heat pumps installations are likely to be classed as ‘permitted development’, meaning there is no need to apply to the local planning department for planning permission however, there are certain exemptions. You should contact your local planning department to check conditions will be met.
A typical ground source heat pump ranges from 6-12 kWp in size and will cost between £14,000 and £19,000.
There are running costs to factor in as well. Heat pumps use electricity to run so your electricity bill will increase (although other energy costs eg on oil, will be saved). The heat output will be more than the electricity input. Where heat pumps are wrongly sized or incorrectly used you may end up paying too much for your electricity, so watch out for this.
Renewable Heat Incentive
Ground source heat pumps are eligible for the Renewable heat Incentive.
You should use an MCS certified installer to install your system. This means that the installer should adhere to technical standards of installation and you can benefit from financial incentives like the RHI.
