Heat Pumps can save energy and money
Have my neighbours done this?
What is it?
An alternative to an electric central heating boiler
What will it save me?
Saves 60-75% of electricty cost compared to on-peak boilers
How do I get it?
Needs to be fitted by a specialist contractor
What does it cost?
Costs around £6-8,000 depending on type (2013)
What are the technical details?
Central heating can also use electricity to heat radiators and the most efficient way to do this is by using a Heat Pump. The process is similar to refrigeration but reversed so heat is extracted from the external environment using a closed system containing a refrigerant.
The heat pump is installed inside the house and acts like a boiler, taking the “free” heat from outside and raising its temperature to pump it through a normal radiator system. There are two main types of heat pumps using different methods to extract the “free” heat.
a. Ground-Source Heat Pumps extract heat from underground either from coils of pipework buried a few meters below the surface or from a narrow, but deep bore hole containing a flow and return pipe. These are very effective because the deep ground temperature rarely drops below 10oC even in winter and this can produce 3-4kWh of “free” heat for every 1kWh of electricity used.
The least cost way is to bury pipe coils, but this would only be possible if there is a large garden that can be used. Boreholes take up little space but a drill rig is needed to create the 80m deep borehole and it's more expensive. This is definitely a specialist job where the installer will sub-contract the borehole work.
b. Air-Source Heat Pumps are an alternative but not quite as efficient, producing 2-3kWh of “free” heat for each 1kWh of electricity. This requires an externally mounted fan unit to extract heat from the outside air and pipe it through to the internal heat pump.
Because the air temperature can drop to well below freezing for periods in winter, it's advisable to have a secondary heating source available when needed. Although there are no ground-works required for the installation of this type of heat pump, it is still a job for a specialist contractor having refrigeration experience.
Hot water can also be provided from a heat pump and this may be stored in a cylinder within the unit or a separate one which would also be fitted with an electric immersion heater.
All heat pumps use electricity and it is important to arrange a suitable tariff from the energy supplier, which may require switching to an alternative provider. There is also a potential income from ground source heat pumps under a government initiative called the Renewable Heat Incentive.