Every autumn the same argument starts in British houses: someone nudges the dial up, someone else nudges it back down, and nobody can say why their number is right. The best heating temperature for a UK home is not a matter of taste or stamina — there is a defensible range, and a second setting on your boiler that matters more than the thermostat does.
The short answer
Set your room thermostat to somewhere between 18°C and 21°C, and start at the low end. For most healthy adults in a reasonably insulated house, 19°C or 20°C in the room where you spend the evening is comfortable. Below 18°C, health guidance starts to become relevant rather than a matter of preference, particularly for older people, very young children and anyone with a heart or lung condition. Above 21°C you are usually paying for warmth you would not notice losing.
The detail that trips people up is that this is a room temperature, measured where the thermostat is — normally a hallway. Hallways run cooler than living rooms, so a hallway thermostat set to 19°C often gives a living room at 20°C or 21°C. If yours sits in a draughty hall by the front door, it will over-heat the rest of the house to satisfy itself.
Why one degree is worth arguing about
Turning the thermostat down by one degree is the most repeated piece of energy advice in Britain, and it is repeated because the arithmetic holds. Space heating is the largest single use of energy in a typical home, and heat loss rises with the gap between inside and outside. A smaller gap, sustained across a whole winter, is a real reduction rather than a rounding error.
What the advice never says is that one degree feels like something. Dropping from 21°C to 20°C is usually unnoticed. Dropping from 20°C to 18°C is noticed immediately, and the household response — a fan heater in one room, or the dial quietly put back up in February — undoes the saving. Go down one degree at a time, live with each for a fortnight, and stop at the first number that feels like a compromise rather than a punishment.
The setting that beats the thermostat: boiler flow temperature
Here is the part most homeowners have never touched. Separately from the wall thermostat, your boiler has a flow temperature — the temperature of the water it sends to the radiators. On many combis it is a dial or menu item marked with a radiator symbol, usually set far higher than it needs to be.
A condensing boiler only condenses — only reaches the efficiency it was sold on — when the water returning from the radiators is cool enough. Run the flow too hot and the return never drops far enough, so you burn gas to produce an efficiency figure that exists only on the datasheet. Turning the heating flow temperature down to around 60°C on a combi is the standard recommendation, and typically recovers several percent of your gas use with no comfort penalty in an averagely insulated house.
If you change one thing this autumn, change the flow temperature, not the thermostat. The thermostat gets the airtime because it is the dial everybody can see, but flow temperature is a one-minute change that costs nothing, needs no trade visit on most boilers, and asks nobody in the house to wear a jumper. It is the closest thing to a free saving left in a gas-heated home.
Two cautions. Hot water is a separate setting and should not be dropped to unsafe levels — leave it alone unless a Gas Safe engineer advises otherwise. And in a poorly insulated house with small radiators, rooms will take longer to warm, so the heating needs to come on earlier rather than hotter.
Room by room: what TRVs are actually for
The thermostatic radiator valves on your radiators are not on/off taps. The numbers roughly correspond to target temperatures, and their job is to stop individual rooms overshooting once the house as a whole is up to temperature.
A sensible pattern: living room and any room where someone sits still for hours at the higher end, hallway and landing lower, bedrooms lower again — many people sleep better at 16°C to 18°C — and unused rooms turned down but not off, so they stay above the point where condensation and mould take hold on cold external walls. Leave the radiator in the thermostat’s room fully open, or the two controls fight each other.
Does any of this change your EPC?
Not the setting itself — an assessment does not care what number you leave the dial on. What it credits is the controls: a programmer, a room thermostat and TRVs together score better than a boiler with a timer and nothing else. If your EPC is being redone before a sale or a remortgage, working controls are worth having installed and demonstrable on the day.
Heat pumps invert this whole conversation, being designed around low flow temperatures and steady running rather than short hot bursts. If that is your system, the advice above needs rewriting rather than adjusting.
What to do in the next 30 minutes
Find your room thermostat and note its current setting. If it is above 21°C, drop it a degree today.
Find the heating flow temperature control on your boiler — the dial or menu item with the radiator symbol — and, on a combi, set it to around 60°C.
Walk round and check the TRVs. Turn down the ones in rooms nobody uses; open the one in the thermostat’s room fully.
Check the timer is not still running last winter’s schedule. Most are.
Take a meter reading and write down today’s date next to it, so you have a baseline to compare against in November.
That last step turns guesswork into evidence. Track winter usage in Home+ alongside your boiler service dates and settings, and by February you will know which of these changes actually paid — rather than repeating the same autumn argument next year.
Frequently asked questions
Is 18°C too cold for a house? It is where comfort advice turns into health advice. For a healthy adult in a jumper, 18°C is workable. For an older person, a baby, or anyone with a heart or respiratory condition, treat 18°C as a floor rather than a target, and keep the room they use in the day warmer.
Does turning the thermostat up make the house heat up faster? No. The boiler runs at the same output either way; a higher setting just means it runs for longer before switching off. Setting it to 25°C to warm the place up quickly only guarantees you overshoot, then open a window.
Is it cheaper to leave the heating on low all day? For most gas-heated homes, no — heating only when you need it uses less. The exception is a very well insulated home, or a heat pump, where steady low-temperature running suits the system better.
What should I set the heating to when I go away in winter? Around 12°C to 14°C on the timer for a short period each day — enough to keep pipes from freezing and hold condensation at bay without heating an empty house.
Where should the thermostat be? An internal hallway or a frequently used room, away from radiators, direct sun, draughts and the kitchen. A thermostat above a radiator switches the system off while the rest of the house is still cold.
My rooms are all different temperatures. Is that the thermostat’s fault? Usually not. More often it is unbalanced radiators, with the ones nearest the boiler taking most of the heat. Balancing is a short job for a heating engineer.
