The Truth About Heat Pumps

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.

7. “Heat pump performance can vary considerably from one installation to another and customer behaviour is a variable that was shown to impact performance.”

Translation: Heat pump performance depends on consumer behaviour as well. Only able and diligent users have a chance of being satisfied with system performance.

8. “Many householders said that they had difficulties understanding the instructions for operating and using their heat pump. This highlights a need for clearer and simpler customer advice.”

Translation: Following on from 7, heat pump systems are a nightmare to understand and operate. Quite likely most householders will be incapable of getting satisfactory results.

9. “A comparison between carbon emissions from heat pump installations and electric or gas heating (based on the U.K. Government’s current predictions for grid decarbonisation) shows that a well installed heat pump can lead to carbon savings, both at present and over the lifetime of the pump.”

Translation: Only well installed heat pumps can lead to carbon savings when you consider both the running and capital costs. Heat pumps may lead to carbon reduction but any improvements will be marginal and not at all certain.

10. “The field trial shows that heat pumps have achieved reductions in heating bills for some customers – especially those whose installations are off the gas grid and are therefore replacing heating fuels such as electricity, LPG and oil.”

Translation: Heat pumps are always very much more expensive to run than mains gas. Even against full-price electricity or LPG, savings are by no means certain.

The report was produced in 2010, so the technology may have improved since. If readers are aware of a more recent trial with better results then let us know in the comments below.

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