Exactly how much you can save will largely depend on your home’s insulation and other characteristics
Octopus Energy says that making a simple switch could save up to £65 on annual heating costs – and it only takes a matter of seconds. The energy company’s advice arrives as millions face higher energy bills, with Ofgem’s price cap rising by 2% from October to December 2025, and an additional 0.2% in January.
Referencing figures from Nesta, Octopus Energy suggested that lowering your ‘flow temperature’ to a maximum of 60°C may be key to saving on these expenses. This setting differs entirely from the number on your thermostat and instead indicates the temperature of water as it exits your boiler.
The energy firm explained: “Set your flow temperature to between 55 and 60 degrees on your combi boiler. Take a look at Nesta’s Money-Saving Boiler walkthrough to see how, depending on your boiler, you could save £65.”
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If you set a thermostat to 15°C, your boiler will heat water to a much higher temperature before circulating it through your home until the room reaches 15°C. According to research by Which?, a typical boiler has a flow temperature set between 75 °C and 80°C, but this is often unnecessary.
In turn, reducing the flow temperature will still allow heat to circulate through your home, though it could mean your boiler uses less gas and runs more efficiently. Despite Octopus Energy’s estimates, the exact amount you will save on this may largely depend on your household’s insulation and unique characteristics.
Delving into different boiler types and how to alter their settings, advice from the Energy Saving Trust also adds: “If you have a conventional boiler with a hot water cylinder, there’ll be just one dial or setting to adjust.
“If you have a combi boiler with no hot water cylinder, there’ll be two dials or settings – one for the radiators and one for hot water. You need to adjust the radiator setting, which you may see as by an icon of a radiator rather than a tap.”
It also suggests: “Before you make any adjustments, it’s a good idea to take a photo or make a note of how everything’s currently set. That way, you’ll know what to turn it back to if you need to. The easiest option is to turn the boiler flow temperature down to a level that’s just warm enough and leave it there.”
Nesta, home of the Money Saving Boiler Challenge, also provides a quick online test to help determine what you can do about your flow temperature. This test takes only a few minutes to complete.
For information, you can access its website here.
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