Is it cheaper to leave the heating on low all day? (UK)

Updated 26 October 2026 · Prices worked out at UK electricity rates

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It is one of the most argued-about questions in British households every winter. The answer from energy experts is fairly clear, but there are exceptions worth knowing.

Short answer: for most homes with a gas boiler and radiators, it is cheaper to heat only when you need it, using a timer and thermostat, than to keep it on low all day. A home loses heat all the time it is warmer than outside, so the longer it is kept warm, the more energy it uses. The main exception is a heat pump, which usually works best running steadily at a low temperature.

Why "on low all day" usually costs more

Heat leaks out of a house through walls, windows and the roof at a rate that depends on how much warmer inside is than outside. Keep it warm for 24 hours and it leaks heat for 24 hours. Heat it for 6 hours and it leaks much less. The extra energy needed to warm the house back up is smaller than the energy saved while the heating was off.

When steady heating makes sense

Heat pumps: they are most efficient at low flow temperatures, so long, gentle running is normal. Follow your installer's advice.
Someone is home all day, for example working from home or caring for a baby or older relative. Then you need heat all day anyway; the question becomes which rooms.
Damp-prone homes: letting rooms go very cold for long periods raises humidity and condensation. A modest minimum temperature can prevent mould. See stopping condensation.

Settings that save money

Set the main thermostat to the lowest comfortable temperature, often 18 to 20°C. Each degree lower saves a noticeable share of heating costs.
Use timer slots for mornings and evenings, starting about 30 minutes before you need the warmth.
Turn radiator valves down in rooms you don't use, but not fully off in rooms prone to damp.
Lower the boiler flow temperature on a combi boiler, following official guidance for your model.
Warm the person, not the house, for short spells: a heated throw or electric blanket costs pennies per hour.

Where to buy (prices change often, so check the current price):

If you only use one room

If the rest of the house can stay cooler, heating just the room you are in can be cheaper. Compare options in our guide to the cheapest way to heat one room.