As the UK moves to a fully electrified energy system, policymakers, regulators and businesses across the energy sector agree that using energy more flexibly will be necessary to manage the grid.

Using energy flexibly will help reduce demand on the grid at peak times, which means that carbon-intensive forms of generation will need to be deployed less often. Individual consumers will play a critical role in this transition by changing how and when they use electricity, resulting in ‘intelligent demand’.

In the short- to medium-term, the two biggest sources of electricity consumption from households are likely to be from electric vehicles and heat pumps. Improving our understanding of the potential to use these technologies flexibly is key to the design of the changing energy system.

Nesta partnered with Centre for Net Zero on HeatFlex UK – a project to pilot and develop a trial to investigate heat pump flexibility, consumer preferences and how these are affected by third-party automation and pre-heating.

This report summarises a small-scale pilot we used to test and refine a heat pump flexibility intervention where we remotely took control of participants’ heat pumps for short periods of time we refer to as ‘events’. Our aim was to reduce their electricity consumption during a two-hour period, while ensuring participants stayed warm and comfortable by ‘pre-heating’ their home before the peak energy demand period began.

The findings and provisional conclusions from our pilot come with the strong caveat that our sample size was too small to support generalisable conclusions. We intend to run a larger trial in winter 2023-2024 which should deliver more robust results.

HeatFlex UK uses a mixed methods approach, incorporating data science, behavioural science and design-led user engagement methods to understand what influences the flexibility potential of heat pumps in homes.

We interviewed participants about their experience of the trial, and used a floor plan of their homes as a prompt for discussion. This gave us insights we might not otherwise have had, such as how different insulation levels in parts of the home, placement of the smart thermostat, and their own behaviour could affect the results. We have also used these floorplans as a way to present these insights

• We found indicative evidence that we were able to move electricity consumption to different points in the day in a way that participants found acceptable.
• We did not find evidence that days with events had different total electricity consumption to days without.
• 9 out of 10 participants reported that the automation of their heating was acceptable.
• Some participants made changes to their heating system to improve their thermal comfort during events such as increasing the flow temperatures to increase the rate of heating during pre-heating windows.
• The majority of temperatures that participants self-reported at the end of the pre-heating window were greater than their normal thermostat setpoints. This suggests broadly that pre-heating worked.
• Some participants changed behaviour to maintain thermal comfort, such as wearing additional clothing or using additional heating sources such as a log burner.
• Interoperability issues prevented some individuals from participating in our pilot and may have made it harder for those who could participate to reduce their demand.

This pilot study gave some indication that the HeatFlex intervention does work as expected, and would be broadly acceptable to consumers. However the sample was too small to state this with confidence. Nesta and Centre for Net Zero will be running a larger scale randomised control trial in winter 2023-24 to further test the intervention.