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HeatFlex UK

heat flex

Identifying how effective heat pumps can be as a flexibility resource

CNZ and Nesta, the UK’s innovation agency for social good, have recently partnered on a new research project. HeatFlex UK is designed to improve our understanding of the potential of heat pumps as a flexibility asset.

Heat pumps are a relatively nascent technology in the UK, but ownership rates are growing. This trial seeks to learn more about how people interact with them and identify the maximum amount of flexibility they could provide without disruption to consumers. This can support the grid during times of strain.

We want to better understand the circumstances in which households would want to participate in heat flexibility events, based on real world data. This can help us design the future energy system in a way that delivers value, convenience and trust to consumers

Why is energy flexibility important?

In a future where we rely on renewables as a larger proportion of our energy mix, we can use the principle of shifting or reducing demand to support the intermittency of supply. Low carbon technologies (LCTs) such as heat pumps and electric vehicles will enable this energy flexibility.

Whilst their increased penetration requires greater flexibility, because of the increased amount of electricity we’ll need to use them, they have ‘controllable loads’. This means we can still adopt these technologies without putting the grid under strain, by using energy at different times.

Furthermore, we may be able to achieve comfort via heat pumps with lower energy consumption. This could mean that we need less overall investment in reinforcing or upgrading the electricity grid. Significantly, this can reduce the overall costs of the energy system and bring down bills for everyone.

Research overview

Right now, domestic flexibility is largely untapped. This is due to limited knowledge on consumer behaviour and challenges in the existing market and regulatory landscape. HeatFlex UK will:

Identify how we can use heat pumps as a flexibility asset to harness as much flexibility as possible from residential consumption. This is balanced against maintaining sufficient comfort and consumer satisfaction

Measure the magnitude of flexibility (kWh curtailed during time windows) that can
be delivered by taking this approach

Test the level of household acceptance of automation to provide grid services and contribute to flexibility

Examine how flexibility capacity varies by household and property characteristics

Experimental heat pump trial

During this trial, we will be controlling households’ heat pumps remotely to assess this technology’s flexibility potential. We’re eliciting people’s thermal neutral zone: the temperature bracket within which a household feels comfortable. We’re then testing if comfort can be maintained whilst we intervene with the operations of the heat pump.

Our ambition is to understand how to achieve customer comfort that’s resilient to many different scenarios. This includes whether it’s a weekday or a weekend, a different time of the day, whether someone is working from home or in the office, and whether the outside temperature is hotter or colder.

By shifting a heat pump’s operation when prices or energy demand is high, we can alter a household’s energy use. This enables them to participate in flexibility services. If we’re to help households do this regularly and at scale in the future, we’ll need help from automation. This can ensure that flexibility happens in the background – requiring minimal manual input from households.

Determining what level of automation ‘works’ for consumers is key. We want to test the level of user acceptability to automation. We also want to assess the extent that customers are willing to allow their heat pump to be controlled remotely, via smart thermostats. These insights are critical to engendering trust in an automated energy system, which will be key to realising the full value of renewable power.

heat flex
heat flex

Want to find out more or get involved?

If you’d like to find out more about this trial, please drop us an email at

What phase is the research currently in?

At the end of last year, we completed the pre-pilot phase and conducted interviews with heat pump owners ahead of the pilot. We used knowledge gathered during these interviews to influence the details of the design of the pilot, which will then inform the design of the trials.

We’ve installed the smart thermostats required to intervene in household heating for those who’ve agreed to participate in the pilot – which began in January 2023 and is running during the winter months. In this phase, we’re analysing the datasets we receive and using key learnings to make adjustments to the full trial design.

In November 2023, our aim is to begin phases one and two of the full HeatFlex UK trial. We’ll be implementing learnings from the pilot to scale up this field experiment to hundreds of consumers – or possibly thousands. We will be using a scheduled plan to harness as much flexibility as possible during times when energy demand is very high over this period.

By scaling up the number of households who participate in this trial, we can more accurately define the parameters of heating comfort zones that can be applied to a diversity of households. We can better understand people’s level of trust in automation; and we can gather more insights about the circumstances in which people want to participate in flexibility events.

By combining these insights, we hope that this research is one step on the journey to outputting an empirical metric that could be used to inform customers, aggregators and the grid about the opportunities to avoid home heating during peak time periods, thereby enabling a greener, flexible future energy system.