The ‘Heat Pump Challenge 2021’ was a citizen science and participative research and discovery project led by Carbon Co-op. We collected feedback and data from around 30 member households currently relying on gas heating to help understand how a heat pump installation would impact their home.
The premise of the challenge was to enable households to simulate, in a limited way, the experience of replacing their gas boiler with a heat pump. This simulation was carried out by reducing the ‘flow temperature’ of boilers, meaning that radiators would operate at a lower temperature, closer to that of a typical heat pump. A secondary benefit of this change is that many boilers will run more efficiently at lower temperatures, in particular newer condensing boilers.
Phase one of the challenge
Over two phases, we helped to develop participants’ understandings of the operation of their boilers, and helped them to reduce the flow temperature, first to 60°C and then to 50°C. At the end of each challenge phase we asked the participants to carry out a survey, about the changes they had made, as well as their experiences and comfort levels in their homes.
“[After reducing my boiler flow temperature] apart from stormy days it was barely noticeable. We did have real success lowering our gas costs and ran the radiators at 43°C according to the boiler settings”
We were keen to emphasise that people should not be jeopardising their comfort, and that all adjustments should only be made so long as people remain comfortable in their homes.
During the collection of feedback, the results started to indicate a dramatic trend. In reducing the flow temperatures to 60°C participants reported that this meant reducing the flow temperature by 5 – 25 degrees, with many boilers previously being set to very high flow temperatures, with only a minority having their flow temperature already at the requested level. Whilst the majority of people were able to participate in this stage, and reduce their boiler flow temperature, several people reported having extremely old boilers with integrated hot water and flow temperature controls, as well as inaccurate temperature controls. These participants were unable to make the reduction in temperature, as doing so would cause an increased risk of legionnaires disease.
Phase two of the challenge
The second phase asked participants to make a further reduction in the flow temperature down to 50°C, and as expected fewer people were able to make this change, either due to their boiler controls themselves, or the impact of the previous phase on the comfort of their home.
However, around half of the participants were able to reduce their flow temperature to 50, albeit often with a noticeable impact on the way their home reacted to heating. For some, this was easily mitigated by slightly extending the heating period, or adjusting radiator valves in colder areas of the house, but for others this was a more fundamental issue which they were unable to resolve without substantial changes to their home – something which would likely need to be resolved prior to the installation of a heat pump.
“[before installing a heat pump] I would insulate more and improve air-tightness as well as find space for a hot-water tank”
In the final survey marking the end of the challenge, more than half (58.8%) of the participants reported that they would be more likely to consider installing a heat pump as a result of taking part, and a further 35% said, that whilst it did not change their perspective on heat pumps, they would be likely to consider installing one in the future. Whilst most people did not consider their home to be “heat pump ready” after taking part in the challenge there was a strong understanding of the kind of measures which would need to be implemented in order to comfortably heat homes using a heat pump instead of gas.
For people who were not immediately looking to make major improvements to their home, many found the performance and efficiency benefits introduced by the challenge of a lower flow temperature to be well worth it, with no noticeable impact on comfort.