The Government-funded Energy Saving Trust has produced a report on a field trial of heat pumps entitled Getting warmer. Mark Ellse has kindly provided a translation of the key findings from the executive summary into plain English.
1. “The performance values we monitored in the sample heat pumps varied widely; the best performing systems show that well-designed and installed heat pumps can operate well in the U.K.”
Translation: Most heat pumps operate poorly in the U.K. Rare exceptions are adequate but only if the systems themselves are well-designed, installed and operated.
2. “The sample of ground source heat pumps had slightly higher measured system efficiencies than the air source heat pumps. The ‘mid-range’ ground source system efficiencies were between 2.3 and 2.5, with the highest figures above 3.0.”
Translation: Ground and air source are equally unimpressive. Though ‘mid-range’ ground source system efficiencies were between 2.3 and 2.5, a third of the systems had efficiencies below 2.0, leading to inevitably high running costs.
3. “The system efficiency figures for the sample of ground source heat pumps were lower than those monitored in similar European field trials.”
Translation: Take no notice of cited efficiencies that are high. Real, measured efficiencies are much lower.
4. “The ‘mid-range’ of measured system efficiencies for air source heat pumps was near 2.2 and the highest figures in excess of 3.0.”
Translation: Real efficiencies are about 2.0, with the worst having efficiencies as low as 1.2. You’d be better off using electric fires.
5. “Heat pump performance is sensitive to installation and commissioning practices.”
Translation: We’ve said it before: even tiny installation errors turn heat pumps into nightmares.
6. “The householders in our field trial sample reported good levels of satisfaction with both space heating and hot water provision. There was no significant difference between users’ satisfaction with ground and air source systems.”
Translation: Even with enthusiastic early adopters, 13% were dissatisfied because of high running costs. But nearly half the social housing tenants were dissatisfied despite the (free) benefits of much improved insulation which came with their (free) heat pumps. Their reason: nightmare running costs.