What Temperature Should My Boiler Be Set at for Hot Water UK

Last updated: April 26, 2024

Are you wondering what temperature should my boiler be set at for hot water UK to save money? Or ensure your combi boiler is running at maximum efficiency?

You should set your boiler to at least 65°C to balance efficiency and warmth.

Setting your boiler’s temperature at this level can improve efficiency. This will help you cut your energy bills while ensuring you stay warm and cosy.

Adjusting the temperature of your boiler can feel overwhelming due to the many controls and settings of boilers and heating systems.

Thankfully, this guide explores the correct temperature for a boiler, how to set it, and what you should know before making adjustments.

What Temperature Should My Boiler Be Set At for Hot Water UK?

Control for adjusting temperature and heating
Image by Worcester Bosch

The Energy Savings Trust recommends setting the temperature of your boiler to 65°C. The setting is suitable for a conventional boiler with a hot water cylinder.

Setting the boiler’s temperature lower than this can make it difficult to heat your hot water to 60°C.

Maintaining the temperature at 65°C or above also ensures the hot water supply to your taps remains safe. It prevents the risk of legionella bacteria developing in the hot water cylinder.

If you have a combi boiler without a cylinder, setting the temperature below 65°C will not affect your hot water. You can find what works for you through trial and error, but a setting of 60°C is reasonable.

Setting the boiler to high temperatures can be tempting if you like things hot.

However, it can overwork your boiler and result in unwanted consequences like a reduced lifespan, more breakdowns, and reduced efficiency.

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.

What Temperature Should My Boiler Be Set At for Radiatior Heating?

For a new condensing combi boiler, the radiator heating or flow temperature should be as low as possible. Flow temperature is the temperature of the water your boiler sends to the radiators.

Water cools as it flows through the radiators before returning to the boiler. Reducing the flow temperature also lowers the temperature of the returning water.

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Lower radiator heating temperatures are an excellent choice if you want to reduce energy consumption and save money on bills. According to the Energy Savings Trust, all boilers become more efficient when the returning water temperature is low.

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. This allows it to recycle heat and return it to your property.

You can reduce radiator heating temperature further for maximum efficiency and increased savings. However, it’s not advised in older properties with poor insulation.

If you live in a new-build property with good thermal efficiency, you may want to try lowering your combi boiler flow temperature to around 50°C.

What Temperature Should My Boiler Be Set At When the Weather Changes?

If you have a combi boiler and the weather or season changes to mild or warm, you can heat your home with low hot water temperatures of around 50°C to 55°C.

The table below shows some appropriate levels you can set, depending on the time of year and your house:

SeasonOld HouseModern House
Jan to Feb60°C to 65°C55°C
March60°C50°C
Apr to Oct55°C45°C
December60°C50°C

Such settings can provide additional efficiency and an ideal balance with comfort. For example, they can help ensure the water at the point of use, such as in taps or showers, isn’t hot enough to cause scalding.

However, depending on your home and heating system, it may limit heating performance. It may take longer to heat your home or get cold sometimes, especially if you’ve not made any insulation or fabric improvements.

Adjusting the temperature constantly through a load or weather compensator can help you limit such risks while benefiting from maximum efficiency.

To use the compensators, you must have a combi boiler and they must be compatible with your system. A heating engineer can help you check this and set them up for you.

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What Controls Should I Have to Set the Temperature?

Using EasyControl to set heating temperature
Image by Worcester Bosch

Understanding your boiler and heating controls is important before answering, ‘What temperature should my boiler be set at for hot water UK?’

Boiler controls help change the temperature of water in the system while heating controls help manage when the heating should be on and what temperature your rooms will be.

Controls that can help you adjust and set the temperature include:

Smart Heating Controls

Smart heating controls are advanced control systems for central heating.

They can do everything from controlling when the heating is on to controlling the heat in your home using thermostats.

Smart controls usually feature internet connectivity and offer various functionalities, including:

  • Temperature and time controls for checking and changing heating and hot water periods.
  • Allowing you to adjust the temperature when you’re not at home or turn the system on or off.
  • Adjusting controls to match your habits. For example, turning the thermostat up or down when temperatures change or heating hot water when you’re likely to shower.

The Boiler Thermostat

Most boilers are fitted with a thermostat that helps set the temperature of the water pumped from the boiler.

The boiler thermostat can be a dial on the boiler unit marked with numbers or a scale from minimum to maximum. some boilers also allow you to control it using buttons with the temperature shown on a digital display.

Combi boilers usually feature two controls for the boiler thermostat. One is for the hot water going to your taps while the other is for the radiator flow.

Regular boilers with separate hot water cylinders usually have one control for hot water taps and radiator flows.

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

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

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Are There Risks When I Adjust My Boiler Temperature?

Adjusting your radiator heating or hot water temperatures can have various unwanted effects. These include:

  • If you turn the boiler thermostat below 65°C on a conventional boiler with a hot water cylinder, you increase the risk of legionella bacteria growing in your cylinder.
  • The house can get too cold when you turn down the temperature, making it dangerous for vulnerable and elderly residents or people with health conditions.
  • Your home may heat up more slowly, or the rooms may not get warm enough or as warm as they used to.
  • You might set the heating controls incorrectly or adjust the settings on your boiler. Before making adjustments, it’s advisable to make a note or take a photo of how everything is set so you know what to turn back if needed.
  • Setting high temperatures can prevent the boiler from entering the condensing mode, limiting its efficiency and performance.

Searches Associated with Optimum Temperature To Set a Combi Boiler

Here are the most common searches for the optimum temperature to set a combi boiler.

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Final Thoughts On What Temperature Should My Boiler Be Set At for Hot Water UK

Knowing what temperature your boiler should be set at is one of the easiest ways to improve its efficiency and save money on heating costs. Setting your boiler to 65°C can provide you with a good balance of efficiency, and performance.

Ensure you familiarise yourself with the boiler’s controls and settings by reading the manual before attempting to adjust the temperature.

Want to learn about all the factors that contribute to a boiler quote? Check out our boiler cost calculator to understand the latest boiler deals and what is factored into a gas boiler replacement estimate.

How old is your boiler? Should you consider repairing the boiler or start looking at the latest boiler prices? It’s no secret that boiler efficiency deteriorates over time.

Sources and References

  • energysavingtrust.org.uk/should-i-turn-boilers-flow-temperature-down/
  • https://www.nhs.uk/conditions/legionnaires-disease/