Nesta published trial findings on 24 October 2025 concluding that heat pump owners on automated type-of-use tariffs such as OVO's Heat Pump Plus could save up to £440 per year compared with a standard variable rate. The trial, run with OVO Energy, remotely altered the heating schedules of 58 OVO customers on the Heat Pump Plus add-on every weekday between 6 January 2025 and 1 April 20251.
Heat Pump Plus gives a flat rate of 15p per kWh on the electricity a heat pump consumes. The trial preheated homes by raising setpoint temperatures by 1C before the peak period, then lowered them by 1C during peak. Nesta reports that on average 30 per cent of each home's space heating electrical demand was shifted away from the 4pm to 7pm peak. In February the preheating period was extended to four hours, from 12pm to 4pm1.
The £440 figure is a potential saving, not a measured one. Nesta states the £443.77 saving is based on an air source heat pump with a UK average seasonal coefficient of performance of 2.8 and annual consumption of 3,689 kWh on the Heat Pump Plus add-on, compared with OVO's average standard variable rate of 27.03p per kWh1. The trial's own treatment group recorded a seasonal COP of 3.64, against 3.65 for the comparison group1.
"These findings mean that heat pump owners could make use of automated type-of-use tariffs such as Heat Pump Plus and potentially save up to £440 per year compared to a standard variable rate."
On comfort, 88 per cent of weekly survey responses reported satisfaction with internal temperatures, 7 per cent were neutral and 5 per cent dissatisfied. Sixty per cent of weekly responses said participants had not noticed a difference in comfort. Nesta reports its results were inconclusive on whether the intervention affected daily COP or total daily electrical consumption1.
The trial used a quasi-experimental matching approach. The treatment group numbered 43 after matching, and the comparison group decreased to 231 households. Nesta reports 58 participants in total, with 57 per cent having had a heat pump for less than a year, and notes that 79 per cent of the account holders involved were male. Domestic hot water was not remotely automated, and participants did not need additional hardware installed1.
| Measure | Treatment | Comparison |
|---|---|---|
| Peak period electricity (kWh) | 2.86 | 2.22 |
| Whole day electricity (kWh) | 21.31 | 21.75 |
| Seasonal COP | 3.64 | 3.65 |
| February and March peak (kWh) | 2.09 | 1.45 |
Source: Nesta, The future of heat1
Why it matters for households
Running costs are one of the two barriers to heat pump adoption Nesta identifies, alongside upfront installation cost. The trial's relevance to a household's energy independence lies in whether a heat pump can be run on a cheaper tariff without the home losing comfort, and whether that can happen without the occupant manually adjusting anything. Nesta reports that most participants did not notice OVO's control, and that participants did not require additional hardware1. The savings depend on the tariff comparison: the £443.77 figure is calculated against OVO's average standard variable rate of 27.03p per kWh, not against a household's actual tariff. Nesta also notes heat pumps currently heat less than 1 per cent of UK households1.
What happens next
The report does not set out dated next steps. Nesta states that households in the trial would feel comfortable allowing continued automation of their heat pumps, although some expected additional incentives1.
Sources1 cited
- The future of heat | Nesta, nesta.org.uk