“What temperature should I set my boiler to?” is one of the questions we’re asked most often in Warwick and Leamington Spa. It sounds simple, but there are really three settings involved, and getting them right makes a difference to both comfort and your gas bill.
The three settings that matter
- Flow temperature: how hot the water is when it leaves the boiler to heat your radiators.
- Hot water temperature: how hot the water at your taps and shower is.
- Room thermostat: the temperature you want the house to reach.
Flow temperature: most boilers are set too high
Many boilers leave the factory, or get left after a repair, with the radiator setting at 70–80°C. In most homes that’s hotter than it needs to be.
Modern condensing boilers are at their most efficient when the water coming back from the radiators is cool enough for the boiler to “condense”, recovering extra heat from the flue gases. That generally means a return temperature below about 55°C. If the flow is set at 80°C, the boiler rarely gets there.
For many homes with properly sized radiators, a flow temperature of around 55–65°C keeps rooms warm in winter. The house may take a little longer to warm up, but the boiler uses less gas doing it. Older houses with small radiators may need it a bit higher on the coldest days, which is fine.
Not sure where to find the setting, or whether your radiators are big enough? Ask us at your next boiler service and we’ll set it up for your home.
Hot water temperature
This depends on your system:
- Hot water cylinder (system or regular boiler): stored hot water should be heated to at least 60°C. That’s high enough to stop legionella bacteria growing in the tank.
- Combi boiler: there’s no stored water, so the same risk doesn’t apply. Set it to a temperature that’s comfortable at the tap, usually somewhere around 50–55°C.
Room thermostat
Around 18–21°C suits most living rooms; many people sleep better at 16–18°C. Turning the thermostat up to 25°C won’t heat the house faster. The boiler works at the same rate either way; it just stays on longer and overshoots.
Don’t heat an empty house
Use your programmer or smart thermostat so the heating comes on about half an hour before you get up and before you get home, and goes off when the house is empty or you’re in bed. If your controls are old or confusing, we fit and set up smart thermostats as part of our central heating work.
When to get it checked
If you turn the flow temperature down and some rooms never get warm, it can point to a radiator that needs bleeding, sludge in the system, or a radiator that’s too small for the room. We’re Gas Safe engineers based in Warwick and can look at it for you.
