The Energy Saving Trust has published a report, Flexible Futures: Integrating smart tariffs with low carbon home technologies, setting out modelled savings from combining clean home technologies with time-of-use tariffs. The report, dated 10 July 2026, modelled more than a million scenarios to test how heat pumps, solar panels and battery storage affect household energy costs in combination with different tariff types1. The trust says some households could reduce annual energy bills by around £800 by combining those technologies with the right smart tariff, based on analysis of multiple tariff types using 2024 energy price data1.
The report's central finding concerns heat pumps and tariff choice. Heat pump users on smart tariffs can save around £330 a year compared to those who are not, yet half of heat pump owners are not currently on one1. The trust says heating costs can fall by up to 80% compared to using gas alone, and that running costs fall further for households that already have solar panels and battery storage1. It also states that its research reveals which tariff types provide the best heat pump savings, and which might actually increase energy bills2.
On upfront cost, the report gives figures for switching to a heat pump. The average cost with no financial support is £11,700; with a government grant in England, Wales and Scotland it is £4,200; and factoring in both the grant and not needing to replace an old boiler it is £5002. The trust says payback periods could be as little as four years, and that it is possible for a heat pump to pay for itself within two to four years2. For the 3.9 million households expected to need a boiler replacement by 2027, it says switching to a heat pump could cost as little as around £500 more than replacing a gas boiler once grants and the cost of a new gas boiler are taken into account1.
"Our new analysis reveals a smarter way to cut costs, with clean home upgrades saving households up to £800 a year when paired with the right tariff."
The trust is calling on the UK Government and Ofgem to introduce policy changes to ensure households have access to more comprehensive, impartial advice, improved tariff comparison tools and greater awareness that smart tariffs can make heat pumps cheaper to run than gas boilers1. It also urges faster progress on flexible tariffs and financial support through the Warm Homes Plan1. Stew Horne, the trust's group head of sector intelligence and external affairs, said people need clearer advice, better tools to compare tariffs and more support to access these technologies1. The report states that tariffs able to unlock these savings are available now, but that there is no tailored advice available to enable consumers to switch with confidence2.
Why it matters for households
The report's figures turn on the interaction between a home's equipment and the tariff it runs on, rather than on either alone. A heat pump on a standard tariff is modelled as costing around £330 a year more than the same heat pump on a smart tariff1, which places tariff choice alongside the installation decision for any household weighing up household flexibility and reward schemes. The trust notes that the energy price cap is set to rise again in October1, so the gap between running costs on different tariffs is the part of the calculation a household can act on without new hardware.
For homes that already have solar panels and battery storage, the report says running costs can fall further again1, which links the case for a heat pump to equipment many households already own. The trust's own framing is that current generic advice is not enough to enable confident, informed decision making2, and its cost figures for a heat pump range from £11,700 without support to £500 where a grant applies and no boiler replacement is needed2. The report does not set out savings by nation, home type or tariff name, and no such breakdown has been reported.
What happens next
The report calls for policy changes from the UK Government and Ofgem on advice, tariff comparison tools and awareness, and for faster progress on flexible tariffs and financial support through the Warm Homes Plan1. No timetable for those changes is given in the report. The trust notes the energy price cap is set to rise again in October1.
Sources2 cited
- Clean tech combo could help beat rising energy bills - Energy Saving Trust, energysavingtrust.org.uk
- How to make heat pumps more affordable - Energy Saving Trust, energysavingtrust.org.uk