Heat pumps are one of the most talked about renewable technologies – on television, in newspapers and magazines. The way they are portrayed they seem to be the answer to all our problems and will suit all properties. But is this true?
Heat pumps (ground, air or water) suit only certain applications and it is important to cut through the marketing spiel and realise this. These units can have large capital costs and can cost you more to run than the system you are replacing if installed in the wrong place.
Three of the key issues to check out before you install are as follows:-
1) Well insulated buildings
As heat pumps are a low temperature device, it is important that buildings that they are installed in are well insulated. Un-insulated buildings require high flow temperatures (the maximum from a heat pump is approx 55 degrees C). Heating to this temperature reduces the efficiency of the heat pump, as the compressor has to work harder to produce the higher temperatures. Add to this, the fact that in a poorly insulated building the heat emitting device, radiators or underfloor, may not be able to provide heat into the building at the low temperatures, so not only are the running costs high, but you also feel cold!
Insulating the building well also reduce the size of the heat pump needed, and the initial capital costs and, in the case of ground source, the amount of ground required.
2) Heating distribution systems
Most existing houses have radiators installed as their heat emitting device. A lot is made of the fact that heat pumps should only be used with underfloor heating. This is not strictly true. However, as radiators require the water to be heated to a high temperature, a heat pump will run up to 25% less efficiently with radiators. In addition, you may need to install larger radiators, to keep warm enough.
3) The fuel you are replacing
Many companies indicate savings can be achieved of up to 50% of your current fuel bills. However what they don’t tell you is that the amount you save depends on the fuel you are replacing and the installation, as we saw above. Different fuels have different costs associated with them. Direct electricity is the most expensive and gas the cheapest. While heat pumps use electricity to drive them, because of their high efficiencies the cost per kWh used can be as much as quartered, if you are currently heating with electricity.
If you have mains gas, the running cost of a well installed heat pump is similar, but as soon as you add radiators or a poorly insulated building into the equation, it pays to stay on gas. However this is likely to change next year if the Renewable Heat Incentive is introduced.
Heat pumps do not suit all applications. You can see that a rambling 17th Century listed building on radiators is not an ideal candidate, neither is an un-insulated building on radiators and the gas main. Do not install a heat pump in a poorly insulated building. However, where the application is correct heat pumps can significantly reduce running costs and carbon emissions making them a worthwhile investment and with the renewable heat incentive the growth of the heat pump market is about to explode.
Written by John Barker-Brown, special projects manager at British heat pump manufacturer Kensa Engineering. First published on www.yougen.co.uk.
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