'Secret' button on boiler hands British Gas, OVO, EDF, Octopus customers free £150

Average bills could go down by as much as 9 per cent by turning your boiler flow temperature down, British Gas, OVO, EDF, EON Next and Octopus customers have been told.

A secret boiler button can slash heating bills by £150, it has emerged. Average bills could go down by as much as 9 per cent by turning your boiler flow temperature down, British Gas, OVO, EDF, EON Next and Octopus customers have been told.

Ben Gallizzi, energy expert at Uswitch.com, said: “The boiler flow rate controls how hot the water is when it leaves the boiler and goes to your radiators. It’s separate to heating and radiator controls. Reducing the flow rate can make your boiler run more efficiently, which can save you energy and money.

“People with a condensing combi boiler may be able to turn down the flow temperature to save themselves some money on their energy bills. For combi boilers, the recommended output temperature for the radiators is 75C and at least 60C for water, which is the temperature that kills legionella bacteria.”

READ MORE Met Office warns UK will wake up to 'notable' weather shift starting today

Which? Energy Editor Emily Seymour said: "Most homes are heated by wet central heating. The heating flow temperature of your boiler is the temperature at which water leaves your boiler on its journey to your radiators. By default, many boilers are set to heat this water to 75-80C. But many homes with condensing combi boilers can be suitably warmed with heating flow temperatures of 60-65°C or lower.

"Lowering that temperature means your boiler uses less gas and operates more efficiently. Combi boilers also let you select how hot the water supplied to your taps is. As a result, you can adjust both your heating and hot water temperature separately.

"Water comes back from radiators into your boiler when it reaches a certain lower temperature, ready to be heated up again. This is called the return temperature. The return temperature is likely to be 60 degrees if you have a flow temperature of 80 degrees."

Emily says: "On a combi boiler, flow temperature for heating is usually shown by a radiator symbol and, for hot water, a tap symbol. Use the up and down arrows to adjust the temperature."