What month should you turn the heating on in the UK?

Most households start in October, but the month matters less than the temperature indoors. When the rooms you use stay below about 18 degrees for several days, turn it on.

What temperature should my house be in winter?

Somewhere between 18 and 21 degrees in the rooms you use is comfortable for most people. Keep it at least 18 if anyone at home is elderly, very young or unwell. Bedrooms can be a little cooler.

Should I test my heating before winter?

Yes. Run it for half an hour on a mild day in early autumn. It shows up stuck pumps, air in radiators, low pressure and valve faults while engineers are still easy to book, rather than on the first freezing night.

Why is my boiler not firing when I turn the heating on?

The usual reasons are the thermostat set below the current room temperature, the timer set to off, low boiler pressure, no power at the boiler, or a lockout with a fault code. Check those in that order.

Do I need to bleed my radiators before turning the heating on?

Only the ones that need it. Run the heating first, then feel each radiator. Any that are cold at the top and warm at the bottom have air in them. Bleed them with the heating off, then recheck the boiler pressure.

When to Turn the Heating On, and What to Check First

There is no correct date to turn the heating on. The sensible trigger is temperature: when your main living rooms are staying below about 18 degrees for much of the day, it is time. In the UK that usually happens some time in October, earlier in a north facing flat or a draughty Victorian terrace, later in a well insulated new build. Anyone elderly, very young or unwell at home should not wait that long. More useful than the date is what you do first. A heating system that has sat idle all summer is at its most likely to fail on the first cold night, when every engineer in London is busiest, so switch it on for a short test on a mild day now, before you actually need it.

The 18 degree rule, and who should turn it on sooner

Around 18 degrees is the figure public health guidance in the UK usually gives as the minimum for a healthy adult in the rooms they use. Below that, especially for long periods, cold starts to affect breathing and circulation. For older people, babies and anyone with a heart or lung condition, the advice is to keep rooms at least that warm and often a little warmer.

So instead of picking a date, put a cheap thermometer in the living room. If it reads under 18 in the evenings for several days running, the heating is due. A room thermostat set to 18 to 21 degrees will then do the rest, only running the boiler when the house actually drops below that.

Before the first cold night: a ten minute test run

Most of the heating faults we see in the first weeks of autumn were there in spring and only show when the system is asked to work. Pumps and valves that have not moved for months can stick, and radiators collect air over the summer. A test run on a mild afternoon finds all of that while there is time to get it looked at.

Check the boiler pressure gauge while the system is cold. Most sealed systems sit around 1 to 1.5 bar cold. If it is near zero the boiler will refuse to run, and if it is up near 3 our guide on boiler pressure too high explains why.
Set the programmer clock and put the heating on for half an hour. Our guide on how to set a heating timer covers dial and digital controls.
Turn the room thermostat up above the current room temperature so the boiler actually fires.
Walk round every radiator after 20 minutes. Cold at the top and warm at the bottom means air, and the radiator needs bleeding. Cold all over may be a stuck radiator valve.
If you have a hot water cylinder, check the hot water still heats with the heating on. The two share a boiler, and a valve that has stuck over summer can leave one working without the other.
Test your carbon monoxide alarm. If you do not have one near a gas boiler or gas fire, fit one.

How to turn the central heating on

On most systems it is three things. First, make sure the boiler has power, which usually means the fused switch next to it is on and there is a light on the boiler. Second, set the programmer or timer to on, or to timed with the times you want. Third, turn the room thermostat up to the temperature you want. If any one of those three is off, the heating stays off.

On a combi boiler there is often also a heating dial or a radiator symbol on the boiler itself. If that was turned right down or switched off for summer, turn it back up. Our guide on what temperature should I set my boiler covers where to set it. If you have a smart thermostat, check the app has not been left in a summer or away mode.

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

For most homes, no. A house loses heat all the time to the outside, and it loses it faster the warmer it is inside. Keeping it warm all day means paying to replace that loss for every hour, including the hours nobody is in. Heating it only when you need it means the house cools while empty, so less heat escapes in total, even though the boiler works harder when it comes back on.

There are exceptions. A heat pump runs best at a low, steady temperature and is usually set up to stay on for long periods. A very heavy, well insulated house with solid floors may cool so slowly that the difference is small. Someone at home all day needs warmth all day anyway. And in a hard freeze, keeping a low background temperature protects pipes in lofts and outside walls. For a typical gas boiler in a London house or flat, though, timed heating with a sensible thermostat setting costs less than leaving it on low.

Should I leave my heating on all day if I work from home?

If you are in all day, the room you work in needs to be warm all day, so yes, the heating needs to be available. The saving comes from not heating the whole house to living room temperature. Turn the radiator valves down in bedrooms and rooms you are not using, keep doors closed, and let the room thermostat hold a steady temperature rather than switching the heating off and on by hand.

Hot water in the heating season

If you have a boiler and a hot water cylinder, the start of the heating season changes how the hot water behaves too. Over summer the boiler may only have run for the cylinder. Once the heating is on, the boiler is running for longer each day, and some households find constant hot water becomes the easier setting. If you rely on an electric immersion over the summer, remember to switch it off once the boiler is heating the cylinder again, or you may be paying to heat the same water twice.

If the radiators come on but the taps stay cold, or the hot water only works when the heating is on, that is a valve or thermostat fault rather than a setting. Our guide to no hot water but the heating works explains how to tell which.

If the heating will not come on

If the boiler will not fire on the first try, check the pressure, check the power, check there is gas at the hob, and look for a fault code on the display before you do anything else. Do not keep resetting a boiler that locks out again straight away. Our guide on no heating or hot water walks through the order to check things in.

If you have done the checks and the heating or hot water is still not working, call us on 020 4652 5111 or send an enquiry. We have 20 engineers across London, which helps when the first cold week of the year arrives and everyone switches on at once. Our rate is on the pricing page and agreed before we attend.

If you smell gas when the heating comes on, do not touch any switches. Turn the gas off at the meter, open windows and call the national gas emergency service on 0800 111 999.

Questions we get asked

What month should you turn the heating on in the UK?: Most households start in October, but the month matters less than the temperature indoors. When the rooms you use stay below about 18 degrees for several days, turn it on.
What temperature should my house be in winter?: Somewhere between 18 and 21 degrees in the rooms you use is comfortable for most people. Keep it at least 18 if anyone at home is elderly, very young or unwell. Bedrooms can be a little cooler.
Is it cheaper to leave the heating on low all day?: For most homes with a gas boiler, no. Heating only when you need it lets the house cool while empty, so less heat is lost overall. Heat pumps are the main exception, as they are designed to run low and steady.
Should I test my heating before winter?: Yes. Run it for half an hour on a mild day in early autumn. It shows up stuck pumps, air in radiators, low pressure and valve faults while engineers are still easy to book, rather than on the first freezing night.
Why is my boiler not firing when I turn the heating on?: The usual reasons are the thermostat set below the current room temperature, the timer set to off, low boiler pressure, no power at the boiler, or a lockout with a fault code. Check those in that order.
Do I need to bleed my radiators before turning the heating on?: Only the ones that need it. Run the heating first, then feel each radiator. Any that are cold at the top and warm at the bottom have air in them. Bleed them with the heating off, then recheck the boiler pressure.