Is turning your boiler’s flow temperature down a good idea?

Turning your boiler’s flow temperature down can help some homes use less energy.

For many condensing combi boilers, around 60°C for radiators is a sensible place to start.

If you’re not sure what to change, LEAP can help you understand your heating controls, bills and next steps.

This question regularly comes up when we are delivering LEAP energy advice around the UK, and it’s not surprising. It’s also a very good tip to know! In many homes, turning the radiator flow temperature down can help a boiler run more efficiently.

Keep in mind that it isn’t a one-size-fits-all rule. The right setting depends on the type of boiler you have, whether you store hot water and whether your home still gets warm enough.

What is a boiler’s flow temperature?

Your boiler’s flow temperature is the temperature of the water it heats before sending it around your radiators. As that water moves through the system, it cools and returns to the boiler at a lower temperature.

That matters because boilers are generally more efficient when the return temperature is lower. In simple terms, lowering the flow temperature can help your boiler work more efficiently and waste less energy.

Is this the same as turning down the thermostat?

No. In fact, this is where people often get confused.

Your thermostat, timer and radiator valves are your heating controls. They decide when the heating comes on and what temperature your rooms should reach. Your boiler flow temperature is different; it controls how hot the water is inside the heating system.

The Energy Saving Trust advises that it’s worth getting your heating controls right first, before you start changing the boiler setting itself.

So, is turning it down a good idea?

For lots of households, yes, it can be worth trying, especially if you have a condensing combi boiler.

According to Money Saving Expert, reducing the flow temperature on a combi boiler can cut gas bills by around £65 a year for some homes. Nesta research shows that turning the flow temperature down to 60°C can improve boiler efficiency by nearly 4%, but savings vary. They depend on what your boiler was set to before, how warm your home already was and whether lower settings still heat your home comfortably.

Simply put, turning the flow temperature down is often a good idea, but there isn’t a magic number that suits every home. It’s better to think of 60°C as a sensible starting point for many combi boilers, not a guaranteed fix.

What temperature should I try?

If you have a combi boiler with no hot water cylinder, around 60°C for radiator heating is usually a sensible place to start. In milder weather, some homes can stay comfortable at 55°C or even 50°C, but it’s normal for radiators to feel less hot and for rooms to take a bit longer to warm up.

If you have a conventional or system boiler with a hot water cylinder, be more careful. The Energy Saving Trust says not to go below 65°C if that same boiler setting is heating your stored hot water, because the cylinder still needs to reach a safe temperature.

How do I change the flow temperature?

On many boilers, you’ll find a dial or button behind a flap. If you have a combi boiler, there are often two temperature settings: one for radiators and one for hot water. The radiator setting is usually marked with a radiator symbol, while hot water is usually marked with a tap.

Before changing anything, take a photo of the current settings. That way, if your home doesn’t feel warm enough afterwards, you can easily put it back the way it was. If you’re unsure what any symbol means, check the boiler manual or get advice on a LEAP energy advice call.

Need help working out what’s right for your home?

If you’re not sure what type of boiler you have, whether your controls are set up properly or whether this change is right for your household, LEAP can help.

A free LEAP energy advice call can help you understand your heating setup, your bills and the practical steps that make the most sense for your home.