Critical juncture: insights from the government’s heat pump research seminar

The government’s heat pump research seminar revealed opportunities to roll out heat pumps for all building types, but studies suggest there is still work to do to ensure optimised performance. Alex Smith and Molly Tooher-Rudd report

The government’s annual heat pump research seminar demonstrated the growing potential for heat pumps in all types of building, while sharing new data and analysis on heat pump performance.

The symposium, held in conjunction with the International Energy Agency (IEA), was opened by Oliver Sutton, low carbon heat technical lead at the Department for Energy Security and Net Zero (DESNZ). He remarked how awareness of heat pumps had mushroomed in recent years, particularly among the general public. 

There had been significant progress in the development of heat pumps, Sutton added, but there was still a lot to do in terms of everyone benefiting from a high-performance heat pump. 

Consultant Roger Hitchin gave an overview of research projects being carried out by the IEA’s Heat Pump Technologies Technical Collaboration Programme (HPT TCP). The UK is one of 20 member countries of the HPT TCP, which is based at the Heat Pump Centre in Sweden.

HPT TCP acts as a forum for the dissemination of UK government-backed research. Sutton is the UK representative on the programme’s executive committee while Hitchin is the UK’s alternate delegate. 

There are a number of current heat pump research projects – known as annexes  – aimed at enhancing performance and addressing barriers to growth (see panel, ‘Heat Pump projects’). One being driven by the UK is Annex 60: Retrofitting heat pump systems in large non-domestic buildings.

Heat Pump projects

Annex 56: Digitalisation and IOT for heat pumps
Report showing comparisons between more than 40 connected heat pump projects. A webinar and slideshow from October 2023 is available.

Annex 57: Flexibility by implementation of heat pumps in multi-vector energy systems and thermal networks
The potential for the use of heat pumps in district heating and cooling, and how they can offer flexibility for electricity grids.

Annex 58: High-temperature heat pumps
Overview of technologies with analysis of case studies. One of the report’s focal points is technologies that can provide process heat above 100°C, a critical requirement for many industrial applications. European statistics show that 67% of the demand between 100°C and 200°C was directly covered by fossil fuels. The first part of the project looking at technologies was published in August.

Annex 60: Retrofit heat pump systems in large non-domestic buildings
Led by the UK, this project aims to provide high-level guidance for buildings owners and other decision-makers. Report due in late 2024.

Annex 61: Heat pumps in positive energy districts
Investigating heat pump solutions for groups of buildings as positive energy districts. Existing clusters will be monitored and evaluated. Report due in 2025.

Annex 62: Heat pumps for multi-family residential buildings in cities
Focusing on heat pump solutions for new and retrofit multi-family houses in high-density cities. Eleven case studies have been added to the website, including four from the UK. The annex is a follow-up to Annex 50 Heat, which has more case studies and was completed in November 2022.

Annex 63: Placement impact on heat pump acoustics
Following on from Annex 51, this project will look at removing acoustic market barriers to heat pumps and will look at acoustics as more heat pumps are used for cooling in a warming climate.

Details of all the projects can be found at

Dr Peter Mallaburn is the project manager for Annex 60 and a principal research fellow at UCL, seconded to DESNZ. He told delegates that it was a big challenge to meet 2050 heat pump targets, especially for non-domestic buildings. 

‘Commercial heat pumps are a hidden problem,’ he said. ‘They don’t get much of the limelight and there is a lack of information out there for those deploying heat pumps.’ 

The aim of the annex is to provide guidance about different systems for those deploying heat pumps. A web-based tool will analyse the requirements of the building owner and offer configurations that would be worth looking at first.

‘It’s complex for decision-makers. There are many complications and issues making it difficult for them to take action, such as capital costs, decisions over energy saving vs carbon saving, compliance, disruption, and risk to reputation,’ said Mallaburn.

The project has gathered 60-70 case studies and the team is looking at how decisions are made during procurement. The guidance will be suitable for all HPT TCP member countries, and will need to look at comparative costs between systems. 

Taking the temperature

Vincenzo Rossi, field data coordinator at DESNZ, spoke about the impact of the UK government’s Help for Households advice to reduce boiler flow temperatures and cut energy bills. The strategy aimed to achieve a 9% saving on bills if the boiler was set to 60oC. The study aimed to find out if householders would be willing to accept lower temperatures and, therefore, be open to making their homes suitable for low-temperature heat pumps . 

To understand if the campaign message hit home, Rossi evaluated the variation of the distribution of boilers with a flow temperature setpoint below, equal to or above 60oC between winter 2021/22 and winter 2022/23. The study revealed that, for a sample of 4,503 boilers over two years, the proportion of households that set their flow temp to 60oC doubled, from 3% to 6%. 

It is predicted the campaign may have impacted more than 400,000 dwellings in England, possibly saving more than £26 million in winter 2022/23.

After the results were collected, a heat map was drawn up to look at the distribution of temperatures, which showed that most of the boilers were set at 72-75oC. It was found that 10% of combi boiler users reduced their setpoint temperature for the entire heating season. The average peak setpoint was reduced from 74 to 70. 

Although flow temperature  was probably adjusted to deal with colder or warmer temperatures, this is not true for households that opted to set their boilers to 60oC. ‘These results can be really useful for heat pump consideration. We can look at behaviour, and how willing people are to live with a system below 60oC,’ said Rossi. 

The findings suggest that, while many users were willing to reduce their temperature from above 60oC to a minimum of 55oC, fewer were willing to lower their thermostats further. 

Suitable for the switch

UCL doctoral researcher Laurence Childs revealed that existing heating systems may be more suitable for heat pumps than previously thought. He analysed data from 4,600 boilers while on secondment at the DESNZ and found that heating systems may be able to operate at lower flow temperatures.

Measurements for the boilers were used to predict if radiator or fabric upgrades were needed for a heat pump to provide the same level of heat as set by the occupants. 

When averaging extracted heat demand over six hours, 31.5% of dwellings could operate at 55°C or less without radiator upgrades. This is three times the amount that was estimated using surveys, suggesting that the costs and disruption of a heat pump could be lower than previously thought, with fewer radiators needing to be replaced. 

Childs noted that averaging heat demand over longer time periods can reduce the requirements for radiator upgrades, which demonstrates the value in changing heating patterns. He said peak flow temperatures were only necessary for a small proportion of the year, which indicates the potential for the installation of small supplementary electric heaters or hybrid heat pumps to reduce the burden of radiator and fabric upgrades. 

The findings could be significant, Childs said, because entire heat distribution systems can cost up to £7,500, creating a significant market barrier to heat pump adoption.

Daniel Logue, adviser at Energy Systems Catapult, was the technical lead on the government’s Electrification of Heat Demonstration Project. Part of the study looked to the technical and practical feasibility of a large-scale rollout of heat pumps across a representative range of housing types and social groups. 

In the project, 742 air source, hybrid and ground source heat pump systems were installed in a range of homes. Only 15% of these homes required a fabric upgrade to enable the heat pump solution, though 93% did have at least one radiator change. 

The seasonal performance factor (SPF) of each system was calculated. While the overall results were positive, Logue said quite a large variation was seen across all heat pump types, indicating that, while many people reported that the systems provided a comfortable temperature, too many were getting a poor-performing system.

Logue suggested that the heat pump model may be one of the reasons for the variation, with newer models, running on R290 refrigerant, outperforming old models running on R410A. However, he highlighted other potential contributory factors, including the quality of the installation and design.  

The study found that heat pumps performed worse if they had a higher flow temperature, but there was no difference in performance between different house types or the age of a property. 

‘All of the homes were deemed suitable for a heat pump. Looking at the results, we can’t say that, because you have an old home, your heat pump won’t run effectively. If the design is done well, there is no reason why they shouldn’t run effectively,’ said Logue, who nevertheless expressed concerns. 

‘Almost all heat pumps performed below what was predicted. Some performed better, but there is a systemic disparity in performance across all of the heat pumps. We saw no correlation between what a customer was told they would get and what was actually achieved, and there was no way of telling which of the heat pumps would perform better’, he said. 

Padraic O’Reilly, engineer at Technological University of the Shannon: Midlands Midwest, reported on the performance of heat pump retrofits installed as part of the Irish Superhomes 2030 project, a joint venture between Electric Ireland and Tipperary Energy Agency. In two research projects, O’Reilly said that heat pumps generally performed well, but he told delegates there were some variations between predicted and actual performance.

In one project looking at the actual performance of 40 heat pumps compared with that predicted in the Irish Building Energy Rating (BER), the team found that, for space heating, the heat pumps produced an average of 12% more thermal energy than had been predicted, while the SPF was 17% lower than had been predicted.

It was a different story for domestic hot water (DHW), with heat pumps using 51% less thermal energy than predicted. The efficiency was also higher. One theory for the DHW performance was that BER software overestimated DHW use.

O’Reilly said one reason for disparities in performance was the lack of a handover to end users, who often don’t understand how to optimise heat pumps. It is essential the skills are in place before embarking on a mass rollout of heat pumps, he added. 

Breaking the sound barrier

Etienne Bailey, senior research officer at DESNZ, summarised the findings of the government’s Independent review of air source heat pump noise emissions, permitted development guidance and regulations.  

Current planning standards put restrictions on the placement, size and noise emissions from heat pumps, but Bailey said the research team felt the evidence for these was limited and that the restrictions may act as a barrier to heat pump uptake. 

‘We found that noise complaints are relatively infrequent compared with the number of installations in the UK, with poor installation a key factor,’ says Dr Antonio Torija Martinez, reader in acoustic engineering at the University of Salford.

Several policy implications were drawn from the research, with recommendations for changes to Microgeneration Installation Standard 020 which will be published shortly. One recommendation is to scrap the rule requiring heat pumps to be positioned one metre away from a neighbour’s wall.

There is an opportunity for consultants to contribute to Annex 60, which is due for completion in late 2024. Researchers are interested in speaking to consultants who have examined the pros and cons of different configurations of retrofit heat pump systems for non-domestic buildings. To find out more, contact Peter Mallaburn at or Roger Hitchin at