Electricity used to cost the same whatever time you used it, unless you had an Economy 7 meter. Smart meters have changed that. Many suppliers now offer tariffs where the price depends on the time of day, and some change every half hour.
Air conditioning and heat pumps are good candidates for these tariffs, because a building holds its temperature for a while. You can cool or warm it a little ahead of time and coast through the expensive hours. This guide explains how that works in practice. We don’t name suppliers or quote rates: tariffs change often, so compare current offers yourself before switching.
How time-of-use tariffs work
The Energy Saving Trust (January 2026) explains that a time-of-use tariff charges different rates by time of day, with electricity usually cheaper overnight when demand is low. Static tariffs such as Economy 7 have fixed cheap hours every day. Smart tariffs can change the price every half hour and need a smart meter that sends readings to your supplier every half hour.
It also warns that if most of your use falls in peak hours (it cites 4 to 7 pm) and you can’t shift it, a time-of-use tariff could cost you more. Check standing charges and any exit fees before you switch.
Why buildings make good batteries
Walls, floors and furniture store heat. A room that has been cooled to a comfortable temperature doesn’t heat up again the moment the system stops; it drifts back slowly, faster in a poorly insulated room and slower in a well-insulated one. That gives you a window to move some of the running time.
- Pre-cooling in summer. Run the air conditioning a little harder before an expensive period, then let it coast or run gently through it.
- Pre-heating in winter. A heat pump can warm the home during cheaper hours and ease off at peak times.
How long you can coast depends on the building, the weather and how much the room gains from sun and people. It’s worth experimenting over a few days and watching the room temperature.
Air conditioning in summer
The good news in summer is that the hottest part of the day is often early to mid afternoon, while many peak periods are late afternoon and early evening. Some practical approaches:
- Set a timer so the system brings rooms down to temperature before the peak period starts.
- Close blinds and curtains on sunny windows to slow heat gain while the system coasts.
- Raise the set point by a degree or two during the peak rather than switching off completely, so the system doesn’t have to fight back from a hot room later.
- If you have solar panels, run cooling when the panels are generating. See our air conditioning and solar panels guide.
Want it done properly? AirCon Doctor installs, repairs and services air conditioning and heat pumps across London and the South East, from our base in East Grinstead. We’re an F-Gas certified company and NICEIC approved. Get a fixed-price quote.
Heat pumps in winter
Heat pumps work best running steadily at low output, so the aim isn’t to switch them off at peak times but to shape the load. Many air-to-water systems let you schedule a higher flow temperature or a hot water cycle in cheaper hours and a setback in expensive ones. Air-to-air systems can use their weekly timers in the same way.
Be careful with deep setbacks. A heat pump that has to recover from a cold house may run at high output in an expensive period, which defeats the point. Modest setbacks usually work better than big ones. Our guide to winter heat pump mode and the running costs guide go into the detail.
Controls that make it easy
Nobody wants to adjust a remote three times a day. Most systems we install can do the work for you:
- Weekly timers built into the controller, with different set points for different periods.
- Manufacturer apps with schedules and, on some models, energy readings.
- Smart home links to platforms that can follow a tariff’s price signals, where the manufacturer supports them.
Our guide to smart air conditioning explains what each brand offers. When we commission a new system we can set up schedules to match your tariff’s cheap and expensive hours.
Businesses and time-of-use pricing
Commercial electricity contracts often have their own day and night rates or peak charges. Offices, shops and surgeries are usually busiest during the day, so there’s less scope to shift cooling, but pre-cooling before opening and sensible set points still help. Larger sites with VRF systems can use central controls to schedule zones. A maintenance contract keeps the system efficient, which saves energy at any tariff.
Does it suit you?
A time-of-use tariff is likely to suit you if you can move a good share of your use into cheaper periods: an EV, a battery, a heat pump with scheduling, or air conditioning that can pre-cool. It’s less likely to suit you if your use is fixed and falls mainly in peak hours. Compare the total cost, including the standing charge, using your own smart meter data where you can.
If you’re planning a new system and want it set up to make the most of a tariff, mention it at the survey. Get in touch and we’ll reply the same working day.
Quick answers
Do I need a smart meter for a time-of-use tariff?
For smart tariffs, yes. The Energy Saving Trust says they need a smart meter that sends readings to your supplier every half hour.
Should I switch my heat pump off at peak times?
Usually not completely. Modest setbacks work better, because recovering from a cold house can make the heat pump run hard in an expensive period.
Can air conditioning pre-cool a house?
Yes. Cooling rooms before a peak period and letting them coast, with blinds closed, shifts some running into cheaper hours.
Which supplier is cheapest?
We don’t recommend suppliers. Tariffs change often, so compare current offers, including standing charges and exit fees, before switching.
Related services
More advice
- How Much Does It Cost to Run Air Conditioning in the UK? 2026 Guide
- Smart Air Conditioning: Apps, Voice Control and Home Automation
- Air Conditioning with Solar Panels: Can They Work Together?
- Air Conditioning in Winter: Using Heat Pump Mode Effectively
- All advice
This guide is general information, checked against the sources linked on 30 October 2026. It isn’t legal, tax or financial advice. Rules, grants and product ranges change, so check the current position before you rely on it.