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Premieres 2 November 2026 at 6pm UK time
The Old Fox's Penny Tips · Episode 6
One Boiler Dial That Could Cut Your Gas Bill
Turning a combi boiler's radiator flow temperature down to 60°C could cut gas use by around 8%, according to Nesta research. General information, not financial advice.
General information, not financial advice. Check your own situation.
- Nesta's Money Saving Boiler Challenge recommends lowering the radiator flow temperature on condensing combi boilers to 60°C, as these boilers work most efficiently when returning water is below about 55°C (Nesta, 'Money Saving Boiler Challenge', 2022–23).
- Nesta's research estimated households could reduce gas use by around 8% by optimising their boiler settings (Nesta project update; Nesta, 'Boiler Campaign – Evidence Summary').
- Homes with a hot water cylinder should keep stored water hot for safety, so get advice before changing settings.
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What the fox said
Is your combi boiler running hotter than it needs to? One dial might trim your gas bill.
Many are set to send water to the radiators at 70 or 80°C.
But a condensing boiler works best when the water comes back cooler, below about 55°C.
Cooler water lets it catch heat that would otherwise escape up the flue.
So the charity Nesta suggests turning the radiator flow temperature down to 60°C.
Look for the heating control with a little radiator symbol. It may be a dial, or buttons.
Its research estimated households could cut their gas use by around 8%.
Turn the radiator dial, not the hot tap one. Rooms may take a little longer to warm up.
This is for combi boilers. If you've a hot water tank, or someone at home feels the cold badly, get advice first.
Try it, and if the house won't stay warm, simply turn it back up. Keep your nose to the wind.
General information, not financial advice. Check your own situation.
Sources
- Nesta's Money Saving Boiler Challenge recommends lowering the radiator flow temperature on condensing combi boilers to 60°C, as these boilers work most efficiently when returning water is below about 55°C (Nesta, 'Money Saving Boiler Challenge', 2022–23).
- Nesta's research estimated households could reduce gas use by around 8% by optimising their boiler settings (Nesta project update; Nesta, 'Boiler Campaign – Evidence Summary').
- Homes with a hot water cylinder should keep stored water hot for safety, so get advice before changing settings.
- Condensing boilers reuse heat that would otherwise escape through the flue, but only when the water returning to the boiler is cool enough (around 54°C or below), so a lower flow temperature helps them run more efficiently (Nesta, 'Boiler Campaign – Evidence Summary'; Money Saving Boiler Challenge).
- On most combi boilers the heating (radiator) flow temperature control is marked with a radiator symbol and hot water with a tap symbol, set with a dial or up/down buttons (Which?, 'One simple way to adjust your boiler to lower your heating bill').
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