Air source heat pumps 3x more efficient than gas boilers, study finds

Real world monitoring has shown that air source heat pumps (ASHPs) can operate with high efficiencies, even in cold weather conditions, according to interim heat pump performance data released as part of the Electrification of Heat Demonstration Project.

Read Electrification of Heat – Interim Heat Pump Performance Data Analysis Report

Funded by the Department for Energy Security and Net Zero (DESNZ), the Electrification of Heat Demonstration Project is working to understand the technical and practical feasibility, and constraints of a mass rollout of heat pumps into British homes.

A total of 742 heat pumps were installed by the delivery contractors – Warmworks, E.ON, and OVO Energy – into a broad spectrum of housing types and ages. These heat pumps are being monitored throughout the trial to assess their performance.

The data show that the median seasonal performance factor in ASHPs was 2.80 (280%), a significant increase of 30-40% since the Renewable Heat Premium Payment scheme (RHPP) heat pump trial was undertaken between 2011-2014.

Innovation in the industry and in the heat pump systems themselves is thought to be a leading factor in this performance improvement.

When the study looked at cold weather performance, it found that on some of the country’s coldest days (where mean daily temperatures fell to as low as -6ºC) there was only a marginal decline in whole system performance. The median ASHP system efficiency was 2.44 (or 244%) on the coldest days of the year.

High temperature ASHPs – those which can achieve flow temperatures similar to that of a gas boiler – were found to provide a viable solution for meeting the heating demand of a property. The high temperature units performed with similar efficiencies to low temperature ASHPs.

Heat pumps in hybrid systems were typically used to meet 32-50% of the space heating demand. They had a median SPF of 2.54 which is lower than standalone ASHPs.

Marc Brown, business leader – homes, at Energy Systems Catapult, says: “The interim findings highlight just how far the industry has come in innovating to improve the performance and efficiency of heat pumps.

“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.”

The interim data and results of this monitoring, conducted between November 2020 – August 2022, has been released by Energy Systems Catapult; the Net Zero Innovation Centre appointed to lead the management contractor consortium.