What Temperature Should You Set Your Thermostat in Winter?
What Temperature Should You Set Your Thermostat in Winter?
What temperature should thermostat be in winter? For most people, between 18°C and 21°C. That is the range the Energy Saving Trust recommends: set your thermostat to the lowest temperature you find comfortable, and for most households that lands somewhere between 18 and 21 degrees. Drop below 18°C and you risk cold, damp rooms and a higher chance of mould; push much above 21°C and you are paying for warmth you will barely notice. This guide explains the room-by-room numbers, what turning it down by one degree actually saves, and the thermostat mistakes that quietly inflate winter bills.
What the Energy Saving Trust recommends for your thermostat
The Energy Saving Trust’s advice is deliberately not a single number. Its guidance says to set your room thermostat to the lowest comfortable temperature for your needs, which for most people is between 18°C and 21°C. The range matters because comfort depends on your home’s insulation, your health and who lives there, but the principle is fixed: find the lowest setting you are genuinely comfortable at, and stop there.
It helps to know what the thermostat actually does. The Trust describes it plainly: a room thermostat keeps your home at a steady temperature. It turns the heating on until it reaches your chosen temperature, then switches it off until the room cools slightly. Two consequences follow. First, turning your thermostat higher will not make your home warm up any faster; it only raises the temperature the system eventually settles at. Second, you do not need to turn the thermostat up when it is colder outside. Your home will heat up to your chosen temperature whatever the weather, though it may take a little longer on the coldest days. Setting the heating to come on earlier in the morning, rather than cranking the dial, is the correct response to a cold snap.
What temperature should thermostat be in winter, room by room
One thermostat sets the target for the whole heating system, but thermostatic radiator valves (TRVs) let you fine tune individual rooms. A widely quoted breakdown, attributed to Energy Saving Trust and World Health Organisation guidance, puts living rooms at around 21°C, bedrooms at 18°C, and bathrooms at 22°C when in use. Treat those as starting points rather than rules, and adjust from the 18 to 21°C band the Trust recommends.
The health floor is the more important number. The World Health Organisation says 18°C is enough for healthy adults, with slightly higher temperatures needed for the very old or young. NHS guidance says you should heat regularly occupied rooms to at least 18°C, particularly where elderly residents or people with medical conditions live. If your household includes older people, young children or anyone with a respiratory or heart condition, aim for the top end of the Trust’s range rather than the bottom.
Practically, that means: keep the living areas where you spend the evening around 20 to 21°C, let bedrooms sit at 18°C (you sleep under a duvet, not on top of one), and use TRVs to keep spare rooms cooler. Your spare room does not need to be as warm as your living room, and turning down radiators in rooms you are not using cuts wasted heat without making the house feel cold.
Why turning it down by one degree matters
This is the finding that surprises most people. The Energy Saving Trust says that if you turn your thermostat down by just one degree, from 22°C to 21°C, you could save £120 a year in Great Britain and £80 a year in Northern Ireland on energy bills (figures quoted in October 2026, reflecting the current price cap). Money Saving Expert cites the Trust’s broader rule of thumb: dropping the temperature by one degree saves around 10% a year on heating for a typical home. Because heating and hot water account for more than half of a typical home’s energy use, that single degree punches well above its weight.
Context helps explain why. Heating your home is really about bridging the gap between the outdoor temperature and your set point. Shaving one degree off a 22°C target removes a meaningful slice of that gap every hour the heating runs, all winter long. Many households have their thermostats set in the 20s without ever testing whether 20 or 21°C feels just as comfortable, so the saving is often free comfort you were giving away.
The flip side is worth stating too. There is little to gain from going below the health floor. National Energy Action and the University of Salford calculated that the difference between heating your home to 18°C rather than 16°C is 84p per day, adjusted for the October 2026 price cap. In other words, dropping to a potentially health-threatening 16°C saves well under a pound a day while raising the risk of respiratory problems, damp and mould. 18°C is the floor, not a suggestion.
These savings land at a useful moment. Ofgem’s energy price cap rose 4% from 1 October 2026, taking the typical dual-fuel bill to £1,723 a year. A one-degree reduction will not erase that rise, but at £120 a year it offsets a real share of it, and it costs nothing to try.
Five thermostat mistakes that waste money
1. Cranking it up to heat the house faster. The boiler puts out the same heat whether the thermostat says 21 or 28. All a higher setting does is keep the heating running longer and overshoot your comfort zone. If the house feels slow to warm, set the heating to come on earlier, not hotter.
2. Turning it up when it is colder outside. The thermostat’s job is to reach the set temperature regardless of the weather. On bitter days the system takes longer to get there, so bring the timer forward by half an hour instead of touching the dial.
3. Heating rooms nobody uses. The classic waste is a toasty spare bedroom and a warm hallway feeding draughts under doors. Turn TRVs down in unused rooms and close internal doors so the heat stays where you are.
4. Blocking the thermostat itself. A room thermostat needs a free flow of air to read the temperature accurately. Tucked behind curtains, buried behind furniture or stuck next to a radiator, it misreads the room and fires the boiler at the wrong times. Keep it clear and away from direct heat sources.
5. Leaving a boiler running low all day. With a gas or oil boiler, the Trust advises it is more efficient, and better for your bills, to have the heating come on when you need it rather than leaving it on low all day. Heat pumps are the exception to this rule, which we cover below. Do not apply heat pump logic to a boiler, or the other way round.
A winter thermostat routine that works
Putting the numbers together, here is a simple daily pattern for a working household:
- Morning warm-up: bring the house to 20°C for the hour or two you are getting ready. Set the heating to come on around 30 minutes before you get up so the house is already warming.
- Daytime: if the house is empty, drop to 18°C rather than heating unused rooms at full comfort temperature.
- Evening: back to 20°C while you are home and active in the living areas.
- Overnight: 18°C is plenty while you are under a duvet. Consider setting the heating to switch off around 30 minutes before bed; the residual warmth carries you through.
Layer TRVs on top: living room radiators up, spare room and hallway radiators down. If you are away for a few days in winter, do not switch the heating off entirely; set the thermostat to around 5°C to protect against frozen pipes, a standard precaution recommended by housing associations each winter.
Heat pump owners: different rules apply
If your home runs on a heat pump rather than a boiler, the on-when-needed logic flips. The Energy Saving Trust notes that with a heat pump you can save money by leaving the heating on all day, because heat pumps work most efficiently delivering steady, low-temperature heat rather than short hot blasts. Heat pump systems also run at lower flow temperatures than boilers, so the thermostat setting interacts with the flow temperature your installer configured. We have a full explainer on whether it is cheaper to leave a heat pump running, and if you are still on a boiler and considering the switch, our 15-minute winter-ready boiler checklist covers the flow temperature setting that pairs with these thermostat habits.
Do not forget the basics around the thermostat
The right setpoint only pays off if the heat stays in the house. Bleed any radiator that is cold across the top so it heats evenly, keep curtains closed at dusk and off radiators, and fit draught excluders around external doors. Insulation is what holds your 20°C in place once the heating clicks off; if your loft insulation is thin, the thermostat works far harder than it should, so check how thick loft insulation should be. And if you keep the house cool to save money, watch for condensation on windows, which is the early warning sign of damp: our guide to stopping window condensation covers the ventilation balance that goes with lower temperatures.
Frequently asked questions
What temperature should my thermostat be in winter at night?
What temperature should thermostat be in winter at night? Around 18°C is the widely recommended overnight setting for winter. You are under bedding rather than relying on room heat, and dropping from an evening 20°C to 18°C overnight trims hours of full-comfort heating. Do not go below 18°C: that is the health floor the NHS and World Health Organisation point to, and colder bedrooms raise condensation risk on exterior walls.
Should I turn the heating off completely when I go out?
For a normal working day, turn the thermostat down to 18°C rather than switching the system off. The house then needs less energy to return to comfort temperature than if it cooled right down, and you avoid the damp that comes with a cold, unheated house. If you are away for several days in winter, set the thermostat to around 5°C as frost protection for your pipes rather than leaving the heating off.
Is it cheaper to leave the heating on low all day?
For a gas or oil boiler, no. The Energy Saving Trust advises that it is more efficient to run the boiler when you need heat than to leave it ticking over all day. For a heat pump, the opposite can be true: steady low-temperature running suits how heat pumps work best. Match the strategy to your system.
What temperature should stop mould and condensation?
Keeping the home at 18°C or above, with regular ventilation, is the standard defence against condensation and the mould that follows it. Cold surfaces plus warm moist air is what creates condensation, so an unheated bedroom with the door shut is a classic mould spot. Extractor fans, trickle vents and drying laundry with ventilation all matter as much as the thermostat number.
Will turning the thermostat up make my house warm up faster?
No. The boiler delivers heat at the same rate whatever the thermostat says; a higher setting only changes the temperature at which the system stops. To warm the house sooner, set the heating to come on earlier. And you never need a higher setting just because it is colder outside.
What temperature should I set for a baby or an elderly relative?
Aim for the top of the Energy Saving Trust’s range, around 20 to 21°C in the rooms they occupy. The World Health Organisation notes that very old and very young people need slightly higher temperatures than the 18°C minimum for healthy adults, and NHS guidance says regularly occupied rooms should be heated to at least 18°C where elderly residents or people with medical conditions live.
Sources
- Energy Saving Trust heating guidance, via Lendology, lendology.org.uk
- Energy Saving Trust thermostat savings figures, via Brit Brief, 22 October 2026, britbrief.co.uk
- Money Saving Expert, energy saving tips, moneysavingexpert.com
- Grimsby Telegraph, central heating temperature guide, grimsbytelegraph.co.uk
- Trust Electric Heating, home temperature and mould guide, trustelectricheating.co.uk
- Incommunities, winter tips and advice, incommunities.co.uk
Related reading
