Understanding how much demand shifting each home with a heat pump can provide will benefit a range of different stakeholders. Demonstrating that heat pumps can be used flexibly could reduce the costs of upgrading the electricity grid to meet future demand. Flexible demand means lower costs for everyone and could make buying a heat pump an even more attractive option to individual households.

Peak times are when electricity demand is very high, usually in the mornings and evenings. When electricity demand is high, it’s more likely that fossil fuel power stations need to be switched on to generate enough electricity to meet demand. Using these more expensive sources of generation increases the overall cost of electricity for consumers and is also bad for the planet.

As more and more homes switch to electric heat pumps the amount of electricity required for heating will increase. But heat pumps could also be part of the solution if they can use energy more flexibly and reduce their demand at peak times. One way this could work is by ‘pre-heating’ a home to a higher temperature before the peak period begins, then reducing the electricity demand from heat pumps when the grid is constrained at times of peak demand.

In the future, households could be paid to reduce their demand when the system needs it. National Grid began trialling this approach in winter 2022. We think flexibility will be more effective if consumers are willing to allow the companies that manage our energy system to control or automate their heating systems remotely.

The technology to use heat pumps flexibly already exists. Nesta and CNZ wanted to better understand how this flexibility can be delivered whilst maintaining household comfort levels and willingness to let someone else take control of their heating system.

In winter 2022-23 we piloted a research method that we have used to inform a large-scale trial for 2023-24. Households participated in “HeatFlex UK events” where we remotely controlled their heat pump via a smart thermostat, to see if we can reduce or shift electricity demand and get feedback on whether their home was still at a comfortable temperature.

Nesta brought user-centred design and behavioural science approaches to this project. We wanted to understand how HeatFlex events may best fit with users’ homes and lifestyles. This also enabled us to test our intervention on a smaller scale, before scaling it up to more households.

In February 2024, we launched our field-randomised controlled trial and conducted 30 HeatFlex events with 43 households (half the households took part in events), where we remotely controlled their heat pumps for four hours.

We aimed to explore three key research areas:

1. Thermal comfort of participants - do we find evidence that internal temperatures were maintained with an acceptable level during events?
2. Acceptability of our intervention (ie, automation of heating systems) - how acceptable do participants find the automation of their heating systems?
3. Demand reduction achieved during events - does our intervention result in changes in household electricity consumption?

Our trial found that householders were happy with the automation of their heat pumps and that internal temperatures stayed within a range that householders were comfortable with.

We found that we were able to shift household demand: we found a statistically significant 32% reduction (0.123 kWh) in household energy consumption during the flexibility period (when we directed the heat pumps to produce less heat).

Overall, our trial demonstrated that automated heat pump flexibility can result in meaningful reductions in household consumption, and could help reduce the impact of a growing need for electricity to heat residential homes in the future.

Read our results in full in our report HeatFlex: the untapped potential of automated heat pump flexibility.