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Oxford University Study Reveals Heat Pump Efficiency in Cold Weather

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Julian Jackson's picture
Staff Writer, Energy Central, BrightGreen PR

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  • Sep 12, 2023

A new study by researchers at Oxford University and the Regulatory Assistance Project thinktank shows that heat pumps outperform fossil fuel systems in cold climates, confounding criticisms that heat pumps are inadequate in subzero conditions.

Even at temperatures approaching -30°C (-22°F), heat pumps are significantly superior in performance to oil and gas heating systems, according to the research from Oxford University. This new study was released as the market for heat pumps rises in many countries as people seek cheaper energy as fossil fuel prices hike. The reduced greenhouse gas emissions from these units are beneficial to both users and governments.

The research, published in the specialist energy research journal Joule, used data from field studies in Europe, North America and Asia. This study showed that at temperatures below zero, heat pumps were between two and three times more efficient than conventional oil and gas heating systems.

Many residential and commercial users in the USA and across Europe would benefit from heat pumps replacing conventional heating sources. But uptake is variable: the UK is lagging far behind leaders like France or Scandinavia, which have installed ten times as many heat pumps as Britain, where there were widely-read media articles disparaging their performance in cold weather.

The report uses examples of studies conducted in extremely cold climates, with temperatures from −10°C (14°F) and approaching −30°C (-22°F). In these temperature ranges, specially engineered “cold-climate heat pumps” are typically deployed. Mitsubishi and Toshiba models tested in Finland at very low temperatures performed well. In the USA testing of cold-climate heat pumps took place in Minnesota and Alaska. The coefficient of performance (COP), the ratio of the useful heat outputted to energy consumed, delivered in these studies was between 1 and 2 at temperatures of −12°C (10.4°F), which is considered to be good performance.

The study, and others, suggest that ordinary air-to-water heat pumps would reliably provide heating across a large belt of moderate-weather USA and most of Europe. The lower running costs and better reliability (fewer moving parts than a boiler), would benefit consumers in the longer term.

Unfortunately, while heat pump uptake increased by 11 per cent in 2022, a combination of public skepticism and insufficient government support means that deployment rates in many countries are lagging behind the levels needed to decarbonize heating and move rapidly towards net zero emission targets.

Authors of the study propose a renewed effort from industry and policymakers to promote the efficiency and effectiveness of heat pumps even in cold weather, warning that the amount of heat supplied by heat pumps in the EU will need to be tripled if the sector is to meet its 2030 climate and energy targets.

"This research should instill confidence in policymakers to provide the right frameworks to roll out heat pumps as rapidly as possible," said Dr Jan Rosenow, director of European Programs at RAP. "The UK has set ambitious targets for heat pump roll-out. 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."

It is clear that incentives need to be created by governments and delivered to consumers to ensure that there is a significant take-up of these heating systems. Currently they are about three times as expensive as conventional boilers, so many consumers simply cannot afford to have them installed, even if running costs are lower. The positive implications of the report show that fears that heat pumps would cease functioning in cold weather are greatly exaggerated.

Harvey Michaels's picture
Harvey Michaels on Sep 13, 2023

This is a flawed study, at least from a New England perspective, which we've been studying.  By applying site heat pump efficiency; noted to be below COP = 2 at 10F, instead of using source efficiency.  In the case where an efficient gas plant produces the electricity used by an additional heat pump, there would still be 50% losses before the electricity arrives at your home.  With an optimistic average 1.8 COP at 10F, that nets to 88% efficient.  Home gas systems can be 95% efficient - potentially more efficient, and less net carbon-emitting in peak winter than electricity.

If you account properly for the marginal cost of electricity on the 200 coldest hours of the year, in means that the electricity a heat pump uses at these times costs $3/kwh or more. Of course, you don't pay it, but your neighbors do in higher rates. 

With our limited grid availability in cold winter, we should only encourage all-electric heating systems in homes that have thermal storage, are highly efficient new or deep-retrofitted, and/or use geothermal. These homes contribute much less to the winter peak.  

We should never, ever use resistance backup. 

But that said - I am sure that we can decarbonize over 90% of winter with heat pumps with economics that are good for the climate, good for the consumer financially, and result in lower rates your neighbor.  The last 10% isn't much - and could easily be a renewable site-tanked fuel, or for now staying on a fossil site-stored fuel like oil or propane, or worst-case pipeline gas; for now - we do need to work ourselves off of pipeline gas, perhaps with community geothermal. But while on gas for backup, using it rather than electric heat in peak winter will save the consumer money, the grid much more money, and reduce carbon emissions as well.



Julian Jackson's picture
Julian Jackson on Sep 15, 2023

Thanks for an interesting and thorough analysis.  I live in the UK, where (in most of the country) we don't have severe winters, so the outcome would perhaps be different than in New England.

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Thank Julian for the Post!
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