Energy Saving
Is It Cheaper to Leave the Heating On Low All Day?
Reviewed by our Gas Safe registered engineers · Last updated 22 July 2026
It’s the heating question everyone argues about. The short answer, backed by the physics and the Energy Saving Trust, is no — for most homes a timed schedule is cheaper. But there are a couple of real exceptions. Here’s the full picture.
Quick answer: For most homes, no — it’s cheaper to heat only when you need it. A house loses heat faster the warmer it is than outside, so keeping it warm all day means paying to replace heat you’re losing around the clock. Heating up from cool costs some energy, but far less than holding the temperature for hours you’re out or asleep. The Energy Saving Trust agrees: use a timer and thermostat. The exceptions are very well-insulated homes and certain heat pumps.
It Depends
Which approach is cheaper for your home
The right answer depends on your home. For most, a schedule wins — but here are the exceptions where low-and-steady can make sense.
| Your situation | Cheaper approach | Why |
|---|---|---|
| Typical insulated house | Timed schedule | You stop paying to replace lost heat while you’re out |
| Poorly insulated house | Timed schedule (and insulate) | It loses heat fast, so on-all-day is very wasteful |
| Very well-insulated, airtight home | Low-and-steady can work | Loses so little heat that reheating barely differs |
| Home with a heat pump | Low-and-steady, weather-compensated | Heat pumps run best at a constant low output |
| Damp or condensation problems | A gentle background temperature | Steady warmth can help control moisture |
The Science
Myth vs physics
The myth
‘It costs more to reheat a cold house than to keep it warm.’ It sounds sensible, but it isn’t how heat loss works — and it’s why so many people overpay by leaving the heating ticking over all day.
The physics
A house loses heat in proportion to how much warmer it is than outside. Let it cool while you’re out and it loses less; you then spend a bit reheating it. Over a day, that’s cheaper than topping up heat you’re constantly losing.
Engineer Insight
Working hard isn’t the same as costing more
The confusion usually comes from a boiler working hard on reheat and people assuming hard-working means expensive. But a boiler running flat out for 30 minutes still uses less gas than one idling for eight hours. The genuine exceptions are two: a very airtight, well-insulated home barely loses heat either way, so it’s a wash; and heat pumps are happiest running low and steady rather than in bursts. For a normal gas-heated house, a good schedule wins — every time.
Costs
Setting up to run it cheaply
Typical North London guide prices — you’ll always get an upfront quote before any work starts.
FAQs
On low all day — your questions answered
Is it cheaper to leave the heating on low all day?
For most homes, no. Heating only when you need it is cheaper, because a warm house loses heat all day and you pay to replace it. The Energy Saving Trust recommends a timer and thermostat over leaving it on constantly.
Doesn’t it cost more to reheat a cold house?
Reheating uses some energy, but less than holding the temperature for the hours you’re out or asleep. The house loses less heat while it’s cooler, which more than offsets the reheat.
When is leaving the heating on low actually better?
In a very well-insulated, airtight home that barely loses heat, and for many heat pumps, which run most efficiently at a low, steady output. For a typical gas-heated house, a schedule still wins.
Can leaving the heating on low help with damp?
A gentle background temperature can help control condensation and damp in problem homes, so a low setback overnight rather than fully off is sometimes worth it — but tackle the cause of the damp too.
What’s the best setup for a gas combi?
A timed schedule set around when you’re home, a comfortable thermostat setting (around 18–21°C), a setback rather than fully off in very cold spells, and a sensible flow temperature so the boiler runs efficiently.
Related
Related guides
Build the schedule that beats on-all-day.
Read guideEnergy SavingHow to Reduce Heating BillsEvery way to spend less.
Read guideEnergy SavingBoiler Efficiency GuideRun the boiler efficiently too.
Read guideEnergy SavingInsulation TipsInsulation changes the maths.
Read guideSmart ControlsSmart Thermostat GuideAutomate the schedule.
Read guideCentral HeatingHow Central Heating WorksWhy a house loses heat.
Read guideBrowse all Energy Saving guides, or head back to the Help & Advice Centre.
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