Is It Cheaper to Leave the Heating On Low All Day?
Last updated 5 October 2026 · Prices based on the Ofgem price cap (October 2026 – December 2026)
This is one of the most searched energy questions every winter. The Energy Saving Trust's long-standing advice is that a timer is cheaper for most homes. Use the calculator below to test it for your own house, then read why heat pumps are the exception.
On low all day vs on and off — cost comparison
Heating on and off with a timer is cheaper here: about £3.93 a day vs £6.80 on gas.
- On low, per day
- £6.80
- Timed, per day
- £3.93
- Difference / winter
- £432
Heat loss scales with indoor–outdoor temperature difference. Gas at 7.97p/kWh, boiler efficiency 88%. Winter figure assumes 150 heating days. Simplified model — heat pumps behave differently.
Which approach suits which home
| Home / system | Better approach | Why |
|---|---|---|
| Gas boiler, average insulation | Timer on and off | Less heat lost while the home is cooler |
| Gas boiler, very well insulated | Either — small difference | Home cools slowly when off |
| Heat pump | Steady low temperature | Heat pumps are most efficient at low flow temperatures |
| Storage heaters (Economy 7) | Charge overnight | Off-peak rate is cheaper |
| Damp-prone home | Keep a minimum of 16°C | Prevents condensation and mould |
What affects the cost
Insulation level
Poorly insulated homes cool quickly, so the timer approach saves more.
Heating system
Heat pumps and boilers behave very differently.
Hours at home
If you are home all day, the difference shrinks.
Outdoor temperature
Colder weather increases the gap between the two methods.
Thermostat setting
Each 1°C lower saves roughly 10% on heating.
How to reduce the cost
- Set the timer to start 30 minutes before you get up or come home
- Use thermostatic radiator valves to heat only used rooms
- Lower the boiler flow temperature to 60°C on a combi
- Keep the home at least 16°C if anyone vulnerable lives there
- Fit a smart thermostat for room-by-room schedules
Frequently asked questions
Is it cheaper to leave the heating on all day?
For most gas-heated homes, no. Heating only when needed uses less energy overall.
Why is a heat pump different?
Heat pumps work most efficiently delivering steady, low-temperature heat, so they are best left running on a low, constant setting.
Does reheating a cold house use a lot of energy?
It uses a burst of energy, but less than the extra heat lost by keeping the home warm all day.
What temperature should I set my thermostat to?
Between 18°C and 21°C for living areas. The NHS recommends at least 18°C for older or vulnerable people.
Should I turn off radiators in unused rooms?
Set them to low (frost or 1–2 on the valve) rather than fully off, to avoid damp.
Sources and methodology
Energy prices come from the Ofgem price cap for Direct Debit customers (GB average). Installation costs are typical UK ranges from installer quotes and industry guidance, rounded. Savings use today's rates and do not predict future prices.