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Heat Pump vs Gas Boiler

Authored by Marco on October 2, 2023

Freezing energy efficiency

Heat Pump vs Gas Boiler: Which is More Efficient in Freezing Conditions?

Griff Thomas, GTEC’s Managing Director and heat pump expert, explores evidence from a new study that disproves one of the great heat pump myths.

“Air source heat pumps (ASHPs) are more than capable of heating UK homes, even on the coldest of winter days. This is the conclusion of a new piece of research from Oxford University and the Regulatory Assistance Project (RAP) analysing ASHP performance data from global ‘mild cold’ climates, including the UK. The results from this study support existing data that shows heat pumps to consistently outperform gas boilers on efficiency.

“The idea that heat pumps do not work in cold weather conditions has been repeatedly reiterated across various media channels in recent years. Often, this is based on subjective beliefs, unverified claims or the opinions of those with an interest in the gas industry. This has led to the UK having some of the worst installation figures in the world. 

Do heat pumps work in the UK?

“Interestingly, one of the co-authors of the study, Dr Jan Rosenow, commented in a Guardian article: ‘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.’

“To achieve top efficiencies across the board, we need to focus on making sure that installations are accurately designed and correctly installed. Let’s provide installers with quality training and interactive design tools that simplify specification and heat loss calculations, speed up surveying and increase accuracy. 

“This study provides key empirical evidence to support the mass roll out of heat pumps in the UK and counter misinformation. Alongside this growing bank of evidence, we need to boost installer confidence, leading to high quality installations, greater energy savings and happy (and warm!) homeowners.”

What did this study look at?

‘Coming in from the cold: Heat pump efficiency at low temperatures’ is published in specialist energy research journal, Joule. It is authored by researchers from Oxford University and the Regulatory Assistance Project (RAP) thinktank. 

By analysing field studies containing real-world performance data from air source heat pumps, the research aimed to address one of the most frequently raised questions surrounding heat pump efficacy – do they work efficiently in cold weather conditions?

Do heat pumps work in cold weather?

Yes! Researchers collated raw performance data from seven field studies covering ‘mild cold climates’ (defined as countries where the average January temperature is above -10°C), including Switzerland, Germany, UK, USA, Canada and China. 

Results showed that:

  • Standard ASHPs consistently maintain a COP of well above 2 at temperatures below 0°C – more than twice the efficiency of gas boilers. 
  • Heat pump efficiency is superior to combustion heating technology even in extreme temperatures. Cold climate ASHPs can perform at COP1.5 at temperatures as low as −30°C. 
How cold is the average UK winter?

According to the Met Office, the number of days where the maximum temperature remains below 0°C has been decreasing since the 1960s and may be lower than many people imagine – just 3.2 days in the UK on average from 2008-2017. 

Additionally, the average coldest day of the year has become milder, from -8.5°C  between 1961 and 1990 to -6.8°C between 2008 and 2017 – an increase of 1.7°C. 

In the study, researchers looked at mean temperatures in January from 1990 to 2020 across the European Union, UK and Norway. They found that:

  • Most winters in Europe, including the UK, are relatively mild with average temperatures above -10°C. 
  • Temperatures ranged from 9.1°C in Portugal to -9.2°C in Finland
  • 80% of European homes are in countries where average temperatures do not drop below 0°C 
  • Only 5% of homes are in countries where average temperatures drop below −5°C. 
Do heat pumps require back up heating?

Generally, heat pump systems in the UK do not require back-up heating. The study found that above −10°C, ASHPs were able to provide the sufficient heat at a high efficiency. In cold climates, ground source heat pumps and hybrid systems will help to ensure adequate heat provision at extreme temperatures.