Heat Pumps (Polar) Bear Up - Nu-Heat Explains Heat Pump Performance

Honiton, United Kingdom, April 16, 2010 --(PR.com)-- Who can forget the images of ‘Frozen Britain’ back in January? As schools closed and the grit ran out, the nation huddled inside snug with their heating systems. Or did they? This was a testing time for heating systems in general, but especially for those relatively new kids on the block, heat pumps. So how did they perform in what were, frankly, Arctic temperatures?

Both ground source and air source heat pumps are said to work efficiently to temperatures as low as - 15°C for air source and -20°C for ground source. With temperatures dropping even lower than that (Altnaharra in Sutherland, reached -22.3°C) the heat pumps had to earn their badge of honour.

Heat pump lowdown

The top 15m of the Earth’s surface maintains an average year-round temperature of 12ºC. Ground source heat pumps (GSHPs) use this heat source to supply the energy required to heat domestic water and a low temperature system such as underfloor heating.

Air source heat pumps work in a similar way, except they extract available warmth from passing air rather than from the ground. In theory they should be able to extract useful energy from the outside air down to temperatures as low as -15°C. The storage cylinder provides both domestic hot water and a boost of heating energy in the coldest weather.


One recent renovation project is sited near to Bodmin Moor in Cornwall, an exposed location where temperatures reached -10°C. During the design stage, the owners had shown reluctance to increase insulation in their 1980s bungalow and wanted to retain radiators in the two bedrooms. Nu-Heat’s solution was a weather compensated heat pump and underfloor heating system using an inverter driven high efficiency external air source heat pump running on an Economy 7 tariff (4.8p/kWh). With this, their first winter using the new technology, householders Mr and Mrs Loom have been thrilled with the results.

Air Source Heat Pump Performance, Bodmin Moor, Cornwall
Energy consumption period Aug 2009 to Feb 2010

Energy supplied to heat pump: 4,106 kWh
Immersion Heater: 0 kWh
Total electricity to heat pump: 4,106 kWh
Energy delivered by heat pump: 15,110 kWh (6,376Kg CO2)

Energy savings from heat pump: 11,004 kWh
CoP of 3.68 for entire Heating and DHW demand

Actual cost of electricity to heat pump 12 months: £402
Comparative cost for Gas: £620 (2,931 Kg CO2)
Comparative cost for oil: £664 (4,004 Kg CO2)

At coastal eco-house ‘Moonraker’ where a ground source heat pump is integrated with underfloor heating, delighted tenants reported the efficiency of the system to owner Dana Schell, describing how they remained warm and cosy as outside temperatures reached -8.5°C, very low indeed for a coastal town.

Another success story was relayed by Nu-Heat’s Technical Director Andrew Grimsley who trials the company’s products at his own home in Devon. His combined system of a ground source heat pump combined with underfloor heating and solar thermal collectors kept the house extremely comfortable.

The Coefficient of Performance (CoP) for both air source and ground source heat pumps will inevitably be lower during such a cold spell, but such extreme conditions are still fairly rare in the UK. In Canada, heat pump technology has been extremely successful in far more testing conditions for many years now. Indications in the UK so far are that heat pump systems can more than handle whatever the British weather throws at us.

Rob McCreedie
01404 549770