What Is The Optimum Temperature To Set A Combi Boiler?

Last updated: November 15, 2023

Are you trying to save money on your heating bills? Or do you simply want to make sure your combi boiler is running at maximum efficiency?

Not surprising considering the latest energy price cap news, but thankfully there are a number of combi boiler settings you can take advantage of to help make your money go further.

What Temperature Should Your Boiler Be?

There is no hard and fast rules when it comes to setting your combi boiler temperature.

It really depends on your own preferences, however with that said there are some general guidelines to follow.

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Radiator Heating Temperature

For a new condensing combi boiler, the radiator heating temperature, also called the flow temperature should be as “low as possible” if you want to maximize efficiency, but bear in mind this isn’t always advised (we’ll explain this in full).

For instance, most boiler manufacturer’s recommend you set your boilers radiator heating temperature at 75°C, but this really isn’t efficient.

In fact, it’s too high for your boiler to to use its “condensing” technology and recycle the lost heat from your flue gases.

Therefore, we recommend reducing your boilers flow temperature to at most 60°C, this will ensure your boiler is operating at 92% efficiency.

Placing your boiler at this setting will put it in “condensing mode”, allowing it recycle that heat and put it back into your property.

If you want to save even more money and make your combi boiler even more efficient you can try reducing your flow temperature even more.

However, bear in mind that this is typically not advised in older properties with poor insulation.

However, if you live in a new build property that has good thermal efficiency you may want to try lowering your combi boiler flow temperature to around 50°C.

Hot Water Heating Temperature

For the combi boiler water heating temperature, its typically advised to set it at 60°C.

In fact, the Health and Safety Executive recommends a hot water discharge temperature of between 35-46ºC so it doesn’t cause scalding but a higher storage temperature of 60ºC to prevent Legionella bacteria.

Typically temperatures exceeding 60°C put your system at higher risk of scale development, so is not recommended.

Additionally, setting the water heating temperature below 50°C increases the risk of legionella disease, so again is cautioned against.

However, there is a lower risk of legionella in domestic dwellings that have a combi boiler (i.e. no hot water cylinder) and where hot water is used on a daily basis.  

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Heard about the gas boiler ban and wondering what the alternatives to gas boilers are? Read our complete guide to replacing your gas boiler with a heat pump.

Wondering how much a new boiler costs? Check out our guide on options available if you need a new boiler but can’t afford it, as well as boilers on finance and government boiler grants here.

Who offer the best boilers deals in the UK? Check out our review of online boiler installation companies, boiler brands and the best UK boilers that topped our list concerning new boilers in the current year.

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