What is the ideal boiler flow temperature for efficiency?
Setting a combi boiler's flow temperature to around 55-60°C (for heating) significantly improves condensing efficiency and can lower gas bills.
Boiler Flow Temperature & Efficiency
Most modern condensing combi boilers are installed with a default flow temperature of 70–80°C, but they run far more efficiently — and condense properly — at lower temperatures.
Recommended Settings
- Central heating flow temperature: around 55–60°C is often sufficient for most well-insulated London homes and allows the boiler to condense more effectively
- Hot water flow temperature: typically kept higher (60–65°C) for hygiene and to avoid Legionella risk in stored hot water
Lowering the heating flow temperature can improve efficiency and reduce gas bills, though the right setting depends on your radiators' size and your home's heat loss. Ask a RARE engineer to review and optimise your boiler settings during your next service.
Reviewed by RARE Plumbing London Engineering Team — Gas Safe registered engineers serving prime London since 2013.
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