Decentralised energy systems of the future will be underpinned by low carbon technologies, including heat pumps in countries with colder climates. Their intelligent use is critical to supporting the grid during times of strain.

Heat pumps are a relatively nascent technology in the UK, but ownership rates are growing. The evidence base for how consumers interact with heat pumps is limited; this field trial was designed to identify an acceptable approach to their remote control that maintains household comfort levels. We have gathered behavioural insights regarding what ‘good’ automation of heat pumps looks like, in order to assess the amount of flexibility we can expect from them in the future - allowing for the design of efficient and consumer-centric future energy systems.

Over a two-year period, we worked with innovation agency Nesta to pilot and then trial an event-based intervention in households. We remotely controlled participants’ heat pumps for a set number of hours during ‘HeatFlex events’ - activating them before and after 'peak periods' and turning them off during that period.

The intervention was innovative for two key reasons: the demand shifting was fully automated, so occupants did not have to take any ongoing action, and it sought to keep household temperatures at an acceptable level by preheating homes.

We hypothesised that the two features – automation and pre-heating – could result in high levels of participation, resulting in a more consistent, widespread amount of demand shifted.

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.

① 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 heat pumps to produce less heat.

② We were able to reduce heat pump electricity consumption: we recorded a 74% reduction in typical heat pump electricity consumption (0.382 kWh) per half-hour during the flexibility window. We believe the above whole-household consumption reduction is smaller in magnitude than the heat pump-specific consumption reduction because many of our participants have solar photovoltaics and batteries.

③ Households were happy with the automation of their heat pumps. Participation in events was high: in only 9% of instances did participants opt out of events before they started

④ Participants were comfortable with the internal temperature of their homes. On average, the internal temperature in the homes of those who took part in HeatFlex events increased by 0.85°C during the two hours when we preheated homes before turning down the heat pumps for two hours. The internal temperature was still on average 0.16°C higher at the end of that second two-hour period, compared to the start of the preheating period.

While the sample was small and not representative of the current population of heat pump owners, our findings show that it is possible to reduce demand by operating heat pumps remotely, without compromising thermal comfort.