Exhaust air heat pumps take a major technical step forward

Variable speed-controlled exhaust air heat pumps save a lot more energy than older models with on/off technology, especially in buildings with a high energy use. This is shown by tests that have been carried out on exhaust air heat pumps by the Swedish Energy Agency.

Exhaust air heat pumps are common in buildings from the 1980s onwards. The buildings have exhaust air ventilation and the heat pump extracts the heat from the indoor air before it is vented. Many house owners are now facing a new choice, because the heat pumps are becoming old and need to be replaced.

"Our tests show that an exhaust air pump with the new variable speed-controlled technology can save up to 65 per cent of the energy used to heat a house compared with an electrically heated house," says Anders Odell, Test Manager at the Energy Agency's Testlab.

The various models tested display major differences in the heat lost for keeping the hot water hot when it is not being used. Some heat pumps have heat losses that are three times as high (no-load losses) as others.

The advice given by the Energy Agency to home-owners who are about to replace their exhaust air heat pumps is to find one that suits their own specific energy requirement. Look also at the pump's Seasonal Coefficient of Performance (SCOP), which shows how efficiently it generates heat and hot water over the period of a whole year.

"The most efficient unit tested has a SCOP of 3.0, which means that for each kilowatt hour of electricity that goes into the heat pump, 3 kilowatt hours of heat come out. Our tests show that modern exhaust air heat pumps are now beginning to approach other types of heat pumps in terms of efficiency," says Anders Odell.

"Energy efficiency improvement in houses is extremely important. Therefore, it is positive that energy-efficient technology is being developed and is winning ground," says Anna Johansson, Acting Unit Manager at Testlab.