Though heat pumps have not until recently been a very high-profile technology, they have become the subject of national conversation in the UK and in countries across the globe. Sceptics often claim that heat pumps are fine when the weather is mild but won’t perform efficiently when the temperature drops below freezing. Are they right?
We, at the Regulatory Assistance Project, have gone through virtual stacks of data on the real-world efficiency of air-source heat pumps across multiple countries and climatic regions to answer that question. Our new research, which draws on the best-available data, shows that, even at -10°C, heat pumps operate at more than twice the efficiency of gas and oil boilers.
The research collected raw performance data from seven different field studies in North America, Asia and Europe, representing a range of climatic zones, heat-pump models and heat-pump configurations. These data sets were analysed for the so-called coefficient of performance – basically, how well a heat pump transforms one unit of electricity into useable heat – in relation to the average outside temperature.
The analysis found that, during freezing temperatures, the coefficient of performance remained well above two in all cases. In other words, these air-source heat pumps operated at more than twice the efficiency of combustion or resistive electric-heating technology. In fact, overall heat-pump efficiency is typically two to three times higher than fossil fuel combustion heating systems well below 0°C.
But what about really cold weather? Our research also shows that cold-climate air-source heat pumps – heat pumps specifically designed for lower temperatures – achieve coefficients of performance above 1.5 in temperatures approaching -30°C. In regions approaching such low temperatures, hybrid heating systems can potentially play an important role: the heat pump provides most of the heating, with another low-carbon heat source complementing the heat pump.
These findings suggest that standard heat pumps are a suitable technical option for almost all of Europe, as heat pumps are a cost-effective provider of heat even throughout the typical European winter. Heat-pump distribution implies consumer satisfaction with the technology: the highest take-up of heat pumps per capita can be found in Europe’s coldest countries, the Nordics. Almost all new heating systems sold in Norway today are heat pumps, with total installation reaching more than 60 heat pumps per 100 households. The majority of these are air-source heat pumps.
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.
The UK government has set ambitious targets for heat-pump roll-out, and is aiming for 600,000 heat pumps to be installed per year by 2028. What is missing is the policy framework to deliver on this ambition. This includes reforming taxes and levies, as well as setting clear phase-out dates for fossil fuel heating. This research should instil confidence in policymakers to provide the right frameworks to roll out this technology as soon as possible.