Air source heat pumps (ASHPs) already plumbed into Britain’s homes are heating them at efficiencies three times greater than conventional gas boilers, even in cold weather, real-life trialling in a government-backed study has proved.

Improved design of devices intended to extract ambient heat from air means they are delivering more heat at lower cost, long-term research funded by the Energy Systems Catapult claims.

With backing from the D-ESNZ energy ministry, sponsors from the Zero Innovation Centre recruited three contractors in logging output and efficiencies for over 700 installed ASHPs through two British winters and a summer up to last August.

On the coldest days, the in-situ equipment averaged output efficiencies of 2.88 times over a twelve month test interval, a 40% rise on a similar mass test in 2014.

The Energy Systems Catapult study found no significant difference between the efficiencies of pumps working at lower or higher temperatures.   The latter process air at temperatures close to those reached by gas boilers.

Air- or ground-sourced pumps with minimal emissions are central to the government’s ambition to strip carbon from Britain’s homes & workplaces by 2035.  Under its £450 million Boiler Upgrade Scheme, the Johnson government last April began offering £5,000 grants in a bid to have 600,000 installed in the nation’s homes by 2027, up from only 35,000 put in during 2020.

After eighteen months of field research, the ESC plans a further series of evaluations.  But Marc Brown the study’s research lead, says it has already slayed one myth, that ASHPs work badly in cold weather.

“With the release of this data, we can finally put to bed the notion that heat pumps do not work in cold weather conditions and that they are inefficient”, said Brown.

“We’ve observed the exact opposite. They are three times more efficient than gas boilers and work in cold weather conditions. Innovation is changing the game in the heating sector.

The ESC research boss called for government and industry to press for more re-training of installers, more promotion and more investment in the technology’s supply chains.

“We’ve done the hard work and demonstrated that heat pumps work”, said Brown. ”The UK is heat pump ready”.

Read the ESC report here.


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