What Temperature Should My Boiler Be Set At? UK 2026

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For most UK homes with a combi boiler, the answer is 60°C for the heating and 50-55°C for the hot water. If you have a hot water cylinder in an airing cupboard, the hot water answer is different and higher — 60°C — for a safety reason we will come to.

That is the short version. The longer one matters, because the question "what temperature should my boiler be set at" has two different answers depending on which dial you are looking at, and almost every boiler in Britain is left set too high on the one that costs you money.

Your boiler has two temperature settings, not one

Open the control panel on a combi boiler and you will usually find two dials, or two numbers on a digital display. One has a radiator symbol. One has a tap symbol.

• The radiator dial is the flow temperature. It sets how hot the water is that goes out to your radiators. This is the setting that decides how efficient your boiler is.
• The tap dial is the domestic hot water temperature. It sets how hot the water is at your taps and shower. This one has almost no effect on your heating bill.

People conflate the two constantly, and a lot of the advice online conflates them too. Turning down the wrong one gets you a lukewarm shower and saves nothing. Turning down the right one saves real money and, done properly, you will barely notice. The rest of this guide takes them separately.

What temperature should my boiler be set at for central heating?

60°C. Lower if your home is well insulated and you want to experiment; 65°C if you have large rooms, small radiators or a poorly insulated house.

Almost every gas boiler installed in the UK since 2005 is a condensing boiler — it has been a building regulations requirement in England and Wales since that year. A condensing boiler has a second heat exchanger that pulls extra heat out of the flue gases by cooling them until the water vapour in them condenses back to liquid. That recovered heat is free, and it is the entire reason condensing boilers beat the boilers they replaced.

Here is the part nobody is told when the boiler is fitted: the condensing only happens if the water coming back from your radiators is below about 55°C. Above that, the flue gases never get cold enough to condense, the second heat exchanger does nothing, and you have an expensive condensing boiler running like a 1990s one.

Return water is typically around 10°C cooler than flow water. So a boiler set to a flow temperature of 80°C is getting water back at roughly 70°C and never condenses. Set it to 60°C, the return is around 50°C, and it condenses for most of the heating season.

Most boilers are commissioned at 70-80°C because that is the factory default and it makes the house warm up fast on the installer's test. It is not the efficient setting.

What the change is actually worth

Holding the amount of heat your home needs constant and varying only the boiler's efficiency, at the Ofgem cap gas rate of 7.97p per kWh:

Based on Ofgem's medium household benchmark of 11,500 kWh of gas a year, all of it burned at 86% efficiency to begin with.

Be sceptical of the "save 9%" headline you will see on this topic, including on some very reputable sites. The arithmetic above gets you about 5% from combustion efficiency alone. The larger field-trial figures — Salford University's boiler trials for Nesta are the ones usually cited — measured whole-system savings, which capture a second effect: a boiler running at a lower flow temperature cycles on and off less often, and every one of those cycles wastes gas purging and reheating the heat exchanger. That effect is real, but it depends heavily on how oversized your boiler is for your house.

So the honest range for a typical UK home going from 80°C to 60°C is roughly £45 to £85 a year. Call it £50-60 for most people. It takes thirty seconds and costs nothing, which makes it one of the best returns in the whole house per pound spent — though insulation saves far more in absolute terms, as our home insulation guide sets out.

What temperature should my boiler be set at for hot water?

This depends entirely on whether you have a cylinder.

Combi boiler: 50-55°C

A combi heats water on demand, so nothing is stored and there is no bacteria risk. Set the hot water dial to 50-55°C.

Any higher and you are heating water you will immediately dilute with cold at the tap — a shower runs at about 40°C and a bath is filled at around 40-42°C. Water leaving the boiler at 65°C just means you use less of it and more cold, and it raises the scalding risk if there are children or elderly people in the house. The saving is small, because most of the gas your boiler burns goes on space heating rather than water, but there is no downside either.

Hot water cylinder: 60°C, and do not go lower

If you have a stored hot water cylinder, the rule changes completely. Set the cylinder thermostat to 60°C.

This is not about efficiency. Stored water between roughly 20°C and 45°C sits in the range where Legionella bacteria multiply. The accepted control measure is to store water at 60°C, which kills them. UK guidance for domestic systems is consistent on this: store at 60°C, and if scalding is a concern, fit thermostatic mixing valves at the taps rather than lowering the storage temperature.

The extra energy is not large. Reheating a 150 litre cylinder from cold to 60°C takes about 7.9 kWh of heat, roughly 69p at the cap rate; to 50°C it is about 6.1 kWh, roughly 54p. But 60°C is the setting, and this is one place where saving 15p is not worth it.

Note that this is the cylinder thermostat — usually a dial strapped to the side of the tank, or a setting on your programmer — not the boiler's own hot water dial. On a system boiler the boiler flow needs to run a little above the cylinder target, so 65-70°C on the boiler is reasonable while the cylinder is calling for 60°C. This is the one legitimate reason to run a higher flow temperature, and decent controls drop it back down once the cylinder is satisfied.

What temperature should radiators be on?

Your radiators sit at roughly the flow temperature, so at a 60°C flow they run at about 55-60°C. Hot to the touch but not scalding — which is where most of the anxiety about this change comes from. People turn the flow down, touch a radiator, decide it is "not working" and turn it straight back up.

The radiators are working. They are delivering less heat per hour, which is a different thing. Radiators are rated to a standard that assumes water averaging 70°C in a 20°C room, and output falls away sharply below that:

This is the most useful table on the page, because it explains both why the change works and why it occasionally does not. At 60°C flow your radiators give about 63% of their rated output. In most UK homes that is still plenty, because radiators are routinely oversized and because your house only needs peak output on the coldest handful of days a year. The house takes longer to reach temperature, then holds it perfectly well.

But if your radiators were already marginal — small rads in a big room, single panels in a solid-walled Victorian house — 63% may genuinely not be enough on a cold night. The answer then is not to give up. It is either to settle at 65°C instead of 60°C, or to reduce how much heat the house needs in the first place. Draught-proofing is the cheapest way to do that and works within a day; loft insulation and wall insulation do more.

How to change the flow temperature on your boiler

The control is on the boiler itself, not on your room thermostat or your app.

• Dial-type boilers (many Worcester Bosch, Baxi, Ideal and Glow-worm models) have a knob marked with a radiator symbol — turn it to around 60°C. Where the dial is marked 1-6 or with a bar graph instead of numbers, roughly two-thirds of the way round is usually 60-65°C and the manual will confirm it.
• Digital display boilers (most Vaillant and Viessmann, and newer Worcester models) need a button press to reach the heating temperature setting, then arrow keys. Look for a radiator icon beside the number you are changing.
• If you cannot tell which dial is which, run the heating and the hot tap separately and watch which number changes. The one that appears when the radiators are on is the flow temperature.

This is a normal user control on every domestic boiler. It needs no tools and does not affect your warranty or service history.

Make the change in September or October, not in January. Your house will take longer to warm up than you are used to, and that is far easier to live with in mild weather while you get used to it.

How to check your boiler is actually condensing

Two checks — and this is where a guide can give you something the dial cannot.

1. Look for the plume. A condensing boiler that is genuinely condensing produces visible white water vapour from its external flue on a cold day, and drips condensate into a small plastic pipe running to a drain. If your flue never plumes in winter, your flow temperature is too high.

2. Measure the return pipe. This is the definitive test. The two pipes into the bottom of the boiler are flow (hot, going out) and return (cooler, coming back). If the return is below 55°C while the heating is running, the boiler is condensing. If it is sitting at 65°C, it is not, whatever the dial says.

A cheap non-contact infrared thermometer (around £13) reads a pipe in a second and is the only way to verify this rather than trust the setting. One caveat worth knowing, because it catches people out: bare copper is shiny, and shiny surfaces fool infrared thermometers into reading far too low. Either aim at a painted or dull section of pipe, or stick a piece of matt masking tape on the pipe and measure that. Pick a model with adjustable emissivity and set it to about 0.95 for the taped reading.

When you should not turn the flow temperature down

Honesty matters more than a tidy conclusion, so:

• Non-condensing boilers. If your boiler predates 2005 and has no condensate drain pipe, there is no condensing gain to unlock. Worse, running an old cast-iron boiler cold can cause corrosion. Leave it alone and put the effort into replacing it.
• Microbore pipework. Homes plumbed in 8mm or 10mm microbore have less water volume to work with and can struggle at low flow temperatures. Try 65°C rather than 60°C.
• You are already cold. If your home does not reach a comfortable temperature at the current setting, lowering the flow temperature will not help. Fix the heat loss first.
• One dial for heating and cylinder. A few older system boilers use a single setting for both. If yours does, the cylinder's 60°C requirement wins and you cannot run the heating at 60°C flow. A competent installer can usually separate the two.

Getting more out of the change

Lowering the flow temperature works best alongside a few other things, roughly in order of value:

1. Turn the room thermostat down a degree, separately. A different lever, and worth more — each degree is roughly 5-8% of your heating energy. 19-20°C is the usual compromise.
2. Let the heating run longer and steadier. Low flow temperature and long run times are the same strategy; short blasts at high temperature are what the change moves you away from. Our guide to whether smart thermostats save money covers the controls side.
3. Fit or fix thermostatic radiator valves. With less heat per hour available, getting it into the rooms that need it matters more. A TRV with matching lockshield is under £10 a radiator, but fitting the valve body means draining the system — a plumber's job for most people. If the radiator already has a TRV body and only the head is seized, a replacement head swaps in two minutes with no draining, which is the fix most people actually need.
4. Balance the radiators. If the far radiator was lukewarm at 80°C it will be cool at 60°C. Balancing with the lockshield valves is free and makes a low flow temperature far more workable.
5. Check the result on a smart meter. A month before and a month after, weather-adjusted, is the only proof that matters — and an in-home display shows gas as well as electricity.

What temperature should my boiler be set at in winter?

The same: 60°C. This question comes up constantly, and the assumption behind it — that the boiler should be turned up when it gets colder — is the wrong model of how heating works.

The flow temperature does not control how warm your house gets. Your room thermostat does that. The flow temperature controls how quickly heat is delivered and how efficiently it is made. On a cold day the heating simply runs for longer at 60°C to hold the same room temperature, and the thermostat decides when to stop.

The one seasonal adjustment worth making is to nudge the flow temperature up during a genuine cold snap if the house struggles to get up to temperature in the morning, then put it back. Better still, if your boiler supports weather compensation — an external sensor that adjusts the flow temperature automatically with the outside temperature — switching it on does the same job properly, and on boilers that already have the hardware it is usually a setting an installer can enable.

Frequently asked questions

What temperature should my boiler be set at for hot water in the UK?

If you have a combi boiler, set the hot water to 50-55°C. There is no stored water, so there is no bacteria risk, and anything hotter simply gets diluted with cold at the tap. If you have a hot water cylinder, set the cylinder thermostat to 60°C — stored water has to reach 60°C to control Legionella bacteria, which multiply between roughly 20°C and 45°C. Where scalding is a concern, fit thermostatic mixing valves at the taps rather than lowering the storage temperature.

Is 60 degrees too low for a boiler?

No, not for the heating side of a condensing boiler. 60°C is where the boiler runs most efficiently, because the return water is then cool enough for the flue gases to condense. Radiators deliver about 63% of their rated output at that setting, so the house warms up more slowly but reaches and holds the same temperature. 60°C would be too low for a stored hot water cylinder, which needs a full 60°C at the cylinder itself for safety reasons.

How much does turning down the boiler flow temperature save?

Going from 80°C to 60°C saves roughly £45 to £85 a year for a medium-usage UK household at the October 2026 price cap. The lower figure is the pure combustion-efficiency gain — 86% to about 90.5%, worth £45.57 on an 11,500 kWh gas bill at 7.97p per kWh. The higher figure comes from field trials that also captured reduced boiler cycling, which matters more the more oversized your boiler is for your house.

Why are my radiators not as hot after turning the boiler down?

Because they are not supposed to be. At 60°C flow your radiators run at about 55-60°C rather than 75-80°C, delivering roughly 63% of their rated output instead of 113%. They are still heating the room, just more gently and over longer. Give it a full week, and judge by whether the room reaches its target temperature rather than by how hot the radiator feels.

Will turning down my boiler affect my hot water or water pressure?

No. On a combi boiler the heating flow temperature and the hot water temperature are separate settings, so changing the radiator dial does not affect your shower at all. Water pressure is not a temperature setting and is unaffected either way. If your hot water has changed, you adjusted the tap dial rather than the radiator dial.

Does a lower flow temperature make my home more suitable for a heat pump?

Yes, and it doubles as a free test. Heat pumps run at flow temperatures of 35-50°C by design, which is why they need a well-insulated home and adequately sized radiators. If your house stays comfortable with the boiler at 55°C, it will almost certainly work on the existing radiators with a heat pump. If it struggles at 60°C, that tells you what to fix first — see our heat pump running costs guide and heat pump cost guide.

The bottom line

Two settings, two answers. Heating flow: 60°C. Hot water: 50-55°C on a combi, 60°C at the cylinder if you have one.

The heating setting is the one worth money, because it decides whether the condensing boiler you already paid for actually condenses. It costs nothing, takes half a minute, and is worth roughly £45 to £85 a year — and unlike most energy advice, it does not require you to be colder. Your house reaches the same temperature, just more gently.

Make the change now while the weather is mild, give it a week before you judge it, and if you want to know for certain it is working, measure the return pipe rather than trusting the dial.