Do you have a combi boiler? Cut your energy use by simply adjusting your boiler settings

Did you know you could cut your gas use by an average of 9% by changing a single setting on your combi boiler?

Turn down the flow temperature on your boiler to 60°C to cut your gas bills without reducing comfort. You could save an average of £178 and up to £267 on your gas bill.

In these difficult times in which we are faced with the cost-of-living crisis, we are all looking for ways to make savings where we can. The good news is that if you have a combi boiler, you can make one easy change which will make it more energy efficient and cheaper to run.

What is a flow temperature and how can I cut my energy use?

The ‘flow temperature’ is the temperature your boiler heats up the water to before sending it to your radiators.

Most gas boilers are set up to operate at what is called an 80/60 flow and return temperature. This means the boiler heats up the water (called ‘the flow’) to 80°C. The water returns to the boiler after travelling around your radiators (called ‘the return’) at 60°C, having given off 20°C to the room. However, an 80/60 flow and return temperature is too high for a combi gas boiler to achieve the A-rated efficiencies shown ‘on-the-box’.

A new campaign ‘Let’s Optimise your Heating’ has been launched by Nottingham Energy Partnership in collaboration with Nesta, to help homes nationwide improve energy efficiency, save on bills and reduce carbon dioxide (CO2) emissions.

To take the boiler challenge and see how much you can save, click here.

How to make the recommended boiler settings

Step 1: Locate your combi boiler

To make the changes, you’ll need to be in front of your combi boiler, not your thermostat. It is likely that the controls will be on the front of your boiler, and they may be hidden behind a flap.

Before you make any changes, it is a good idea to take a picture of the current settings of your boiler controls – just in case you would like to change them back.

Step 2: Find the radiator symbol

Depending on the manufacturer of your boiler, the symbol for central heating should look something like the examples to the right. Your combi boiler will have this symbol next to one of its dials or on one of its buttons.

If you see a dial, check step 3a. If your radiator has buttons, check step 3b.

Step 3a: Adjusting the radiator temperature using a dial

The temperature that we are aiming to set the radiator at is about 60°C.

Most combi boilers don’t have the temperature displayed around the radiator temperature dial, so you won’t be able to see the exact temperature. The diagram on the left shows the approximate position you should adjust the dial to set your radiator at 60°C – you can aim for roughly 12 o’clock.

If your radiator temperature is already below 60°C, we recommend that you keep it at the current temperature.

Step 3b: Adjusting the radiator temperature with buttons

First, press the button with the radiator symbol on or near it. On the display, this should show the current radiator temperature. Using the down or minus button, set the radiator temperature to 60°C. The images on the right show how this might look depending on the manufacturer of your boiler.

If your radiator temperature is already below 60°C, we recommend that you keep it at the current temperature.

If you are struggling to alter your settings, has a variety of different boiler manuals. You can search by the manufacturer and model of your boiler, or your boiler’s GC number. Every boiler has a GC number, and it’s usually on the front of the boiler. It starts with ‘GC’ followed by a 7-digit number. Within the manual, there will be guidance on how to alter your radiator temperature.

For a step-by-step guide, click here.

How does adjusting my boiler settings save money?

By reducing the flow temperature, you will be using less gas to heat your home because you will be heating the water that flows between the boiler and the radiator to a lower temperature.

Most boilers have an 80/60 flow and return temperature, sending a temperature of 80°C to your radiators, giving off 20°C to heat your home and returning 60°C to your boiler. By reducing the flow temperature, you can achieve the same effect without losing that 20°C.

Don’t worry, this doesn’t affect the temperature of your hot water and doesn’t mean you will have to take cold showers, it means that you will be setting your boiler into ‘condensing mode’.

What is condensing mode?

Condensing mode is when the boiler starts to recover its lost heat, running more efficiently. This means that you will be setting your boiler to run at the efficiency rating that many modern combi boilers advertise.

Reducing the flow temperature can achieve significant carbon reductions and lower running costs by an average of 9% on gas bills without losing warmth. Based on Ofgem’s average energy bill of £3549, of which £2,220 will be for gas.

Will my house feel colder?

You shouldn’t feel a difference. Your radiators may feel cooler to the touch, but this is because the water being sent to the radiators is cooler. They will still heat your home effectively; it may just take a little longer. For many, this is not a noticeable difference, and can be easily resolved by setting your heating to come on 15-30 minutes earlier than before.

Over 15 million households in the UK have a combi boiler – if we all work together to turn down our boilers, then we can make a huge difference during a time when we are hoping to reduce our energy bills, lower our energy use and prevent energy loss.

For more information and support regarding the cost of living, click here.