What temperature should my boiler be set at? 

Updated on 5th November 2026:

Kieran Haig

Technical Repair Engineer, British Gas

There isn’t a one-size-fits-all when it comes to boiler temperature. The temperature you should set your boiler to depends on what type of boiler you have. 

Find out the ideal temperature for different boiler types, so you can safely and comfortably warm your home. 

What is boiler flow temperature?

Boiler flow temperature is different from room temperature:

• Boiler flow temperature is the warmth of the water in your boiler before it travels to your radiators
• Room temperature is how warm the air is in your room

How does boiler flow temperature work?

Your boiler warms water before sending it to your radiators to heat your home. This water is eventually sent back to your boiler, but it’s cooled down by then to what’s known as the return temperature.

Lowering the flow temperature of your boiler also reduces the return temperature. A lower return temperature can help a condensing boiler work more efficiently. 

Just be careful not to set the flow temperature too low, as your radiators might not get warm enough to heat your home properly. 

What temperature should my boiler be set to?

The temperature your boiler should be set to depends on the type of boiler you have. 

Combi boilers

A combi boiler heats water straight from the mains rather than storing it in a hot water cylinder. This means you get hot water instantly, without waiting for a tank to heat up. 

For the radiator flow temperature, around 60°C is a sensible starting point. 

System and regular boilers

System boilers and regular boilers typically have a separate hot water cylinder. Your boiler needs to be hot enough to heat the cylinder safely. 

A cylinder thermostat measures the temperature inside your hot water cylinder and switches off the central heating once it reaches a set temperature. The cylinder thermostat should be set to around 60°C. 

Why lower your boiler temperature?

Improved efficiency

Lowering the flow temperature can help a condensing boiler operate more efficiently because it reduces the return temperature. 

Potentially lower energy use

Lowering the flow temperature of your boiler could make it more efficient. This could reduce the amount of energy you use and potentially cut down your energy bills. 

Of course, the amount of energy you could save can depend on:

• Your previous boiler setting
• The size of your home
• How insulated your home is
• Your heating system
• The weather
• How long your heating system operates
• Your desired room temperature. 

Can I turn my boiler temperature down too far?

A lower temperature isn’t always better. If the flow temperature is too low:

• Your radiators may not get hot enough
• Your rooms may take longer to reach your desired temperature
• Your home may feel cold, especially during winter
• A regular/system boiler may not heat its water cylinder sufficiently. 

Every home and heating system is different, so it may be worth adjusting your settings until you reach your desired temperature.  For a boiler with a hot water cylinder, going below the recommended 65°C flow temperature could increase the threat of Legionella bacteria.

How do I change my boiler temperature?

Step 1: Identify your boiler type

Is it a combi, system or regular/conventional boiler? If you’re not sure, check for extra tanks and cylinders. 

Step 2: Find the correct control

The control may have:

• a radiator symbol 
• a tap symbol 
• a numbered dial 
• digital controls. 

Step 3: Check the manufacturer's instructions

This is important as controls can differ between boiler models.

Step 4: Make gradual adjustments

For a combi boiler with radiators, 60°C is a reasonable starting point. But you may want to modify the temperature gradually. 

Step 5:  Monitor your home

If rooms aren't reaching a comfortable temperature, the flow temperature might need increasing.

What temperature should my room thermostat be?

A room thermostat controls the temperature of your room, rather than the temperature of the water inside the boiler. The Energy Saving Trust recommends setting your thermostat to the lowest comfortable temperature. For many people this is between 18–21°C.

Once the room reaches your ideal home temperature, the thermostat tells the heating to switch off. This helps prevent your heating system from using more energy than it needs to. 

Turning the thermostat higher won’t make your boiler heat the room faster. If your home is taking a long time to heat, adjusting the boiler flow temperature may be more relevant than simply increasing the thermostat.

What temperature should my hot water be?

Homes with a hot water cylinder

The cylinder thermostat should be set to at least 60°C. The boiler may need to be set to 65°C to achieve this. This is important for controlling the growth of legionella bacteria. 

However, your tap water should be set to a lower heat than your water tank. It should be a maximum temperature of 50°C to avoid the risk of scalding. 

Homes with combi boilers

Combi boilers have separate hot water temperature and flow temperature settings. The hot water for a combi boiler should be set to around 50°C to reduce the risk of scalding. 

Need repairs?

Have no heating or hot water? Book a boiler repair before 11am with British Gas and get a local engineer out to your home the same day. 

Based on Sept 2025 - Aug 2026 data, 83% of customers who contacted before 11 am received a same-day service.