Answer first
It is worth testing, not assuming. Download your half-hourly smart-meter data, model the tariff against your real use and check the peak rate as carefully as the advertised off-peak rate.
Heat pumps suit steady operation, so tariff optimisation should protect comfort and efficiency. A small setback, planned hot-water window, solar or battery may help. Repeatedly switching the heating hard on and off can be counterproductive.
Smart time-of-use tariffs rely on communicating half-hourly meter data
View sourceCommon evening peak period highlighted for household-use checks
View sourceAverage heat-pump electricity reduction during the two-hour turn-down window in a 43-home trial
View sourceDiscuss heat-pump costs and savings for your home
Share your postcode, current heating and the bill question you want answered. FLO can explain what needs measuring before any saving figure is treated as realistic.
Start with your load shape
A standard single-rate tariff charges the same unit price throughout the day. A time-of-use tariff varies it. Savings depend on the proportion of electricity used in cheap periods and avoided in expensive ones—not on the cheapest headline price alone.
Download at least several weeks of half-hourly data, including cold weather if possible. Then apply every tariff period, standing charge and any export rate. A supplier calculator can help, but retain the assumptions so two offers can be compared.
Move flexible loads before compromising heating
EV charging, a dishwasher, battery charging and some hot-water production may be easier to shift than space heating. Deal with those first. The building itself can store some heat, but the safe amount depends on fabric, comfort and the system.
Energy Saving Trust advises that time-of-use tariffs are worth exploring for households with heat pumps, EVs or batteries, while warning that fixed use can reduce the benefit. A working smart meter that sends half-hourly readings is required.
- Cheap and peak unit rates
- Standing charge and exit terms
- Your winter half-hourly profile
- Hot-water and legionella schedule
- Battery power as well as capacity
- Whether the tariff can change or be withdrawn
Preheating can work, but the trial result is not an annual saving
A Nesta and Centre for Net Zero trial remotely preheated 43 homes for two hours, then turned heat pumps down for two hours. During that turn-down window, average heat-pump electricity fell by 74% and average total household electricity by 32%. Internal temperature remained, on average, 0.16°C above its starting point at the end.
That demonstrates short-period flexibility, not a 74% annual bill saving. The financial value depends on tariff spread, rebound consumption, weather and how often events occur. Any automated control should keep the household informed and allow an override.
Do not fight weather compensation
A heat pump is often most efficient when it supplies the lowest water temperature that keeps the home comfortable. Deep stop-start scheduling can force higher temperatures during recovery and undo some tariff benefit.
Use the installer’s commissioned curve and a modest setback as the starting point. If the house cools rapidly or misses target temperatures, fix the design or control issue rather than relying on expensive boost operation.
Run an annual comparison before switching
Model a representative year where possible, then stress-test a cold week. Include non-heating electricity because a tariff applies to the whole meter. Check whether solar export, battery charging or EV rates interact with the heat-pump terms.
Review the first month after switching and again after winter. A tariff that looked attractive in summer may behave differently once heating dominates the load.
What to read next
Related answers and services
Questions people also ask
Do I need a battery for a heat-pump tariff?+
No, but a battery can move electricity across tariff periods. Its cost, losses and power limits still need to be justified.
Should I heat the house only in the cheapest hours?+
Usually not. Heat pumps commonly work best with longer, steadier operation. Use measured flexibility and modest setbacks rather than a boiler-style twice-daily schedule.
Can my installer choose my tariff?+
Your supplier contract is your decision. An installer can explain expected consumption, while you compare current tariff terms using your household data.
Evidence used for this answer
Figures are explained in context and links go to the independent source. Prices, tariffs, scheme rules and standards can change, so check the source again before making a financial or technical decision.
- Energy Saving Trust: time-of-use tariffsHow half-hourly smart tariffs work, when flexibility helps and what to compare before switching.
- Energy Saving Trust: the most efficient way to run a heat pumpGuidance on weather compensation, longer run periods, setbacks, radiators, hot water and smart energy use.
- Energy Saving Trust: low-carbon technology and tariff combinations2026 research on the interaction between heat pumps, solar, batteries and time-of-use tariffs.
- Nesta: remotely controlled heat-pump flexibility trialResults from a 43-home trial using two hours of preheating followed by a two-hour turn-down period.