Last updated: 4 November 2026. Prices are Ofgem’s averages for 1 October to 31 December 2026. General information, not professional heating advice.
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It’s the question that splits households every winter: is it cheaper to leave the heating on low all day, or to put it on a timer and only heat the house when you need it? Someone in every family swears that “it costs more to warm a cold house back up”, and someone else is creeping around turning the thermostat down.
I have a PhD in materials chemistry and I spent years teaching science, so heat loss is one of my favourite topics. Here’s the short answer, the science behind it in plain English, the important exceptions, and what it actually costs.
Quick answer: For most UK homes with a gas boiler, no, it isn’t cheaper to leave the heating on low all day. Using a timer and thermostat to heat your home only when you need it uses less energy. The Energy Saving Trust calls the idea that it’s cheaper to leave it on low all day “a complete myth”. The main exceptions areheat pumps, homes with damp problems, and anyone who needs to stay warm all day for health reasons.
Why heating on low all day costs more (the science, simply)
Your home is always leaking heat to the outside, through walls, windows, the roof and the floor. The key fact is this:
The warmer your home is compared with outside, the faster it loses heat.
So whenever your home is warm, you’re paying to replace heat that’s escaping. If you keep it warm all day, even at a low temperature, it’s losing heat all day, and your boiler is replacing that heat all day.
When the heating goes off, your home cools down. As it cools, the gap between inside and outside gets smaller, so it loses heat more slowly. When the heating comes back on, yes, the boiler has to work hard for a while to warm things up again. But in total it uses less energy than keeping the house warm for all those extra hours.
Think of a leaky bucket. Keeping it full all day means pouring water in constantly. Letting it empty and refilling it when you need it uses less water overall, even though the refill takes a big pour.
That’s why the Energy Saving Trust’s advice is to heat your home only when you need it, using a timer and thermostat. (Which?, quoting the Energy Saving Trust)
What heating costs right now (winter 2026)
Ofgem’s price cap sets the maximum unit rates on standard variable tariffs. For 1 October to 31 December 2026, the average Direct Debit rates in England, Scotland and Wales are:
| Unit rate | Daily standing charge | |
|---|---|---|
| Gas | 7.97p per kWh | 29.68p |
| Electricity | 26.32p per kWh | 54.83p |
(Ofgem) Gas includes 5% VAT. Electricity has no VAT in Great Britain from 1 October 2026 to 30 June 2027, following the October Budget extension.
Two things jump out:
- Gas is roughly a third of the price of electricity per unit. Heating with a gas boiler is usually much cheaper per hour than plug-in electric heaters.
- Every hour of heating you don’t need is money saved. That’s why timers make such a difference.
A quick example: a 2kW electric fan heater running for an hour uses 2kWh of electricity. At 26.32p per kWh, that’s about 53p an hour. Run it for 5 hours an evening and it’s over £2.60 a day. Heating one small room with a plug-in heater can make sense for short spells, but it’s an expensive way to heat a house. You can check your own figures with my Ofgem energy price cap calculator.
When leaving the heating on low CAN make sense
Here’s where it gets more interesting. There are times when a low, steady temperature is the right choice:
1. You have a heat pump
Heat pumps work differently from gas boilers. They’re designed to run for long periods at a low flow temperature, and they’re most efficient that way. Turning one off and on like a boiler can make it work harder. If you have a heat pump, follow your installer’s settings and the manufacturer’s guide rather than general boiler advice.
2. Your home gets damp or mouldy
Cold homes get condensation, and condensation leads to mould, which is bad for health. If your home is prone to damp, keeping it a little warm (rather than letting it go very cold) and ventilating well can help. A cheap indoor thermometer and humidity monitor (ad) shows you when the air is getting too damp.
3. Someone at home needs to stay warm all day
The NHS advises heating the rooms you use regularly to at least 18°C, especially if you have a health condition. It lists people over 65, babies and children under 5, pregnant women, and people with long-term health conditions, disabilities or mental health conditions among those most at risk from the cold. (NHS: keep warm, keep well) If someone at home falls into these groups, staying warm comes first. Use the tips below to make that heat go further, and check the help at the end of this post.
4. In a big freeze, to protect your pipes
If temperatures drop well below zero and you’re going away, don’t switch the heating off completely. Use your boiler’s frost setting or a low thermostat setting so pipes don’t freeze and burst. A burst pipe costs far more than a few days of low heating.
5. Storage heaters
If you have electric storage heaters on an off-peak tariff, they charge up overnight and release heat during the day. That’s how they’re meant to work, so the “timer” advice doesn’t apply in the same way. Check your heater and tariff instructions.
How to set your heating to save money
These are the settings the Energy Saving Trust suggests (I checked them in detail for my 100 ways to save energy at home guide):
- Set your thermostat between 18°C and 21°C, at the lowest temperature you’re comfortable with. The Energy Saving Trust estimates turning it from 22°C to 21°C could save around£120 a year.
- Use a timer. Switch the heating on about 30 minutes before you get up and off about 30 minutes before bed. Your home stays warm for a while after the boiler stops.
- Use your radiator valves (TRVs). Set them to 3 or 4 in the rooms you use most, and 2 or 3 in bedrooms. Turn them down in rooms you don’t use, but not off if damp is a problem.
- Don’t turn the thermostat up to “heat faster”. A thermostat isn’t an accelerator. The boiler heats at the same speed; setting 25°C just means it carries on past the temperature you wanted.
- Heat the person, not just the room. On a cold evening, a heated throw (ad) or electric blanket uses far less electricity than heating a whole room.
- Stop the draughts. A door draught excluder (ad), thick curtains closed at dusk, and furniture moved away from radiators all keep the heat you’ve paid for.
Heating on vs off: a quick comparison
| Low all day | Timer when needed | |
|---|---|---|
| Energy used (gas boiler) | More | Less |
| Comfort when you’re home | Steady | Warm at set times |
| Best for | Heat pumps, damp homes, someone home all day who needs warmth | Most homes where people are out for part of the day |
| Risk | Higher bills | Cold if the timer doesn’t match your day |
The right answer is often a mix: a timer for the main heating, a slightly warmer setting in the room where someone spends the day, and the frost setting in a freeze.
Help with heating costs this winter
If you’re worried about keeping warm, check what you’re entitled to:
- Warm Home Discount: £150 off your electricity bill if you’re eligible. See my Warm Home Discount guide.
- Winter Fuel Payment: for people of State Pension age. See my Winter Fuel Payment 2026 post.
- Council crisis support: many councils help with energy costs. My free money help UK guide explains what’s available.
- Your energy supplier: if you can’t afford your bills, Ofgem says you can ask your supplier for a payment plan, a payment break or help from a hardship fund. Also check yourDirect Debit isn’t set too high.
- Priority Services Register: free extra support from your supplier and network if you’re older, disabled, have a long-term health condition or young children.
Heating on low: people also ask
Is it cheaper to leave the heating on low all day UK?
For most homes with a gas boiler, no. A home loses heat faster when it’s warm, so keeping it warm all day uses more energy than heating it only when you need it. Heat pumps and damp homes are the main exceptions.
Does turning the heating on and off cost more?
No. Warming a cold home back up takes a burst of energy, but it’s less in total than keeping the home warm for all the hours you didn’t need it. Using a timer is usually the cheapest way to run a gas boiler.
What temperature should I set my heating to?
The Energy Saving Trust suggests between 18°C and 21°C, at the lowest temperature you’re comfortable with. The NHS advises at least 18°C in the rooms you use regularly, especially if you’re older, very young or have a health condition.
Should I leave the heating on at night?
Most people don’t need to, as long as the bedroom stays at a safe temperature. Switching off about 30 minutes before bed is usually enough. If someone in your home is vulnerable to the cold, keep their room warm overnight.
Is it cheaper to leave a heat pump on all the time?
Heat pumps are designed to run steadily at a low temperature, so they’re often set to run for long periods. Follow your installer’s advice and your manufacturer’s guide for the best settings.
Should I leave the heating on when I’m on holiday in winter?
In very cold weather, use your boiler’s frost setting or a low thermostat setting so pipes don’t freeze. You don’t need to keep the house warm, just above freezing.
Is it cheaper to use an electric heater than central heating?
Per unit, electricity costs about three times as much as gas right now. A plug-in heater can make sense for one small room for a short time, but heating your home with gas central heating is usually cheaper.
Summary
- Is it cheaper to leave the heating on low all day? For most gas boiler homes, no. Use a timer and thermostat.
- Homes lose heat faster when they’re warmer, so extra hours of heating mean extra cost.
- Exceptions: heat pumps, damp homes, people who need warmth all day, freezing weather (use the frost setting) and storage heaters.
- Set your thermostat between 18°C and 21°C, heat only the rooms you use, and stop draughts.
Next step: go through my 100 ways to save energy at home and tick off the free ones this week.
General information only. I’m a scientist, not a heating engineer. For problems with your boiler or heat pump, speak to a Gas Safe registered engineer or your installer.
Sources (checked 4 November 2026): Official source for corrected claim · Ofgem: price cap rates by region · Energy Saving Trust: thermostats and controls · Which?: central heating wars (Energy Saving Trust quote) · NHS: keep warm, keep well · Ofgem: help if you can’t afford your energy bills