Heat pumps are more than twice as efficient as fossil fuel heating systems in cold temperatures, according to a major new study.

A landmark paper from Oxford University and the Regulatory Assistance Project (RAP) think tank – Coming in from the cold: Heat pump efficiency at low temperatures – reveals that heat pumps outperform oil and gas heating, even at temperatures near -30°C.

The paper, published in the scientific journal Joule, is based on research gathered from studies across Europe and North America. The comprehensive research gathered raw performance data from seven field studies focusing on heat pump efficiency in mild cold climates.

The data represents a range of climatic zones, heat pump models, and heat pump configurations from Switzerland, Germany, the UK, the US, Canada, and China.

The paper’s authors say: “A question frequently raised is how well [heat pumps] perform when temperatures drop below freezing, as some commentators and the media have repeatedly suggested that heat pumps cannot deliver useful efficiencies at lower temperatures…

“[This paper] finds that well below 0°C, heat pump efficiency is still significantly higher than fossil fuel and electric resistive heating systems at an appliance level…

“In extreme cold climates, such as where the lowest temperatures approach −30°C, performance data have shown that heat pumps can provide heat at efficiencies up to double that of resistive heating.”

The studies analysed for the Oxford University/RAP commentary uncover two key findings – first, standard air-source heat pumps can maintain average coefficients of performance (CoPs) between 2 and 3 in mild cold climates and, secondly, cold-climate air-source heat pumps can see CoPs above 1.5 even in extreme low temperatures.

Heat pumps work well in UK climate

As most European countries experience milder winters with typical minimum temperatures above −10°C, the analysis suggests that heat pumps can be successfully installed in these conditions without concerns over performance or the need for back-up heating.

Dr Jan Rosenow is a principal director of European programmes at the RAP as well as an honorary research associate at Oxford University’s Environmental Change Institute and was one of the paper’s authors.

In an article for the New Stateman that coincided with publication of the paper, she pointed out: “Clearly, the UK, with its mild winters, is very well-suited to deploying heat pumps, as real-world performance data shows. Claims that heat pumps won’t perform efficiently when it’s cold are unsubstantiated; the best available data shows the opposite.

“Heat pumps have rightly been identified in multiple net zero scenarios as the key heating technology for decarbonisation. This new research supports the effectiveness of heat pumps in cold weather, confirming their superior efficiency compared with fossil fuel heating systems.”

Heat pump misinformation

Dr Rosenow told The Guardian newspaper: “There has been a campaign spreading false information about heat pumps [including casting doubt on whether they work in cold weather]. People [in the UK] don’t know much about heat pumps, so it’s very easy to scare them by giving them wrong information.”

The Guardian and investigative journalism organisation, DeSmog, recently claimed that lobbyists associated with the gas boiler sector had attempted to delay a government measure to boost the uptake of heat pumps.

Other studies have reinforced the value of heat pumps operating in cold climates. For example, building occupiers as far north as Alaska are using heat pumps to keep their homes comfortable in the winter, according to Yale Center for Environmental Communication, part of the Yale School of the Environment, Yale University in the US.

Meanwhile, Energy Systems Catapult – a body designed to ensure businesses and consumers capture the opportunities of clean growth – has released encouraging data from its field monitoring. This shows heat pumps are three times more efficient than gas boilers and that their median coefficient of performance (CoP) on cold days is 2.44, compared to 2.80 on a year-round basis.

Marc Brown, interim business leader of Energy Systems Catapult, said: “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 to run”.

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