Interim performance data released as part of the Electrification of Heat Demonstration Project (EoH), has shown that air source heat pumps (ASHPs) operate with high efficiency even in cold weather conditions, making the technology “a viable domestic retrofit solution three times more efficient than gas boilers.”
Funded by the Department of Business, Energy and Industrial Strategy (BEIS) the project created a representative sample of British households by installing 742 heat pumps in a range of homes in partnership with delivery contractors, Warmworks, E.ON and OVO Energy.
Seasonal Performance Factor improvements
The interim data collected from monitoring these homes between November 2022 and August 2022, showed that the median Seasonal Performance Factors (SPFs) for ASHP systems was 2.80 (280%).
SPFs relay the in-situ efficiency of a heat pump system over the course of 12 months.
The interim data shows an SPF increase of roughly 0.3-0.4 (30-40%) from the Renewable Heat Premiums Payment scheme (RHPP) which ran from 2011 to 2014.
Despite the increased efficiency of heat pumps, Energy Systems Catapult warned that the performance variation of heat pumps remains high. This, the not-for-profit centre of excellence suggested, indicates that the consistency of heat pump design needs to be addressed.
The project also discovered that heat pump performance was only marginally affected by cold weather.
The median efficiency for a ASHP on the coldest days of last year (falling as low as -6oC) was 2.44 (244%), representing a less than 15% drop.
High temperature ASHP performance
High temperature ASHPs can achieve flow temperatures similar to a gas boiler, making them an attractive solution for meeting the fluctuating demands of heating a property, with the added benefit of reducing the need for a deeper retrofit.
The study found that high temperature ASHPs perform at a similar efficiency level as their low temperature counterparts, only demanding higher temperatures when its colder outside. These weather controls however, rarely demanded higher temperatures during the project’s time period.
Its efficiency, paired with the less intrusive installation process, broadens the variety of buildings that ASHP units are a viable option for.
Hybrid Heat Pumps
Hybrid heat pump systems are heat pumps that are paired with a fossil-fuelled heating system e.g. a gas boiler.
These systems are designed to run ‘cost-optimally’ by deciding to operate either the boiler or heat pump in accordance with fluctuating energy prices/demand.
The performance data showed that these systems typically met 39% of space heating demand.
The median heat pump efficiency however was lower that ASHPs at 2.37 (237%), giving an overall estimated heating efficiency of 1.26-1.42 (126-142%).
“The interim findings of the Electrification of Heat Demonstration Project highlight just how far the industry has come in innovating to improve the performance and efficiency of heat pumps, said Marc Brown, business leader – home at Catapult.
“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. 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.
“While we’re taking steps in the right direction, we should not grow complacent. At the risk of sounding like a broken record, innovation and training are critical to the success of a mass rollout of heat pumps. We’ve done the hard work and demonstrated that heat pumps work – the UK is heat pump ready. Now we need to apply those learnings. Government and industry should commit to investing in upskilling existing installers in low carbon heating solutions and doing more to attract new talent into the sector.
“This should be coupled with public and private investment in innovation to help transform the sector and deliver on our Net Zero ambitions, without losing sight of the consumer. Get this right and we can be a world leader in green heating solutions.”
