Adjusting your boiler's flow temperature to reduce energy expenditure and lower bills
In the pursuit of energy efficiency and comfort at home, John Small, home energy expert and owner of Ty Eco, recommends a tailored approach to finding the right boiler flow temperature.
Boiler flow temperature refers to the temperature your boiler heats water to before sending it to your radiators. Adjusting the flow temperature on a combi boiler can be done by locating the temperature controls on the front and using the plus and minus buttons or the dial.
The recommended boiler flow temperature for energy efficiency and comfort typically ranges around 60–65°C for most homes. However, older homes with poorer insulation may require higher flow temperatures during colder months to maintain comfort, since heat loss is greater. In contrast, well-insulated new builds often allow for lower flow temperatures while maintaining comfort, which improves efficiency by reducing boiler workload and fuel consumption.
Seasonally, in warmer months or shoulder seasons, reducing boiler flow temperatures can enhance energy efficiency without compromising comfort as heating demand lessens. In winter, higher temperatures closer to or slightly above 60°C might be required to meet heating loads in poorly insulated homes.
For homes with underfloor heating systems, flow temperatures are generally lower—typically between 30°C and 45°C—since underfloor systems operate effectively at lower temperatures than radiator-based systems.
In summary:
- Older homes (less insulation): Boiler flow temps near 60–65°C during cold months; possibly higher if very cold.
- New homes (good insulation): Boiler flow temps can be kept lower, closer to 55–60°C or even below in mild weather.
- Time of year: Lower flow temps in mild or shoulder seasons; higher temps in deep winter.
- Underfloor heating systems: Lower flow temps, around 30–45°C.
For older homes, John Small recommends aiming for around 55°C in warmer months and closer to 60°C in the winter. Consulting the boiler's manual or a qualified engineer is recommended when adjusting the flow temperature.
Lowering the boiler flow temperature could save the average household around £65 a year, as explained by John Small. The Money Saving Boiler Challenge by Nesta can be a trusted guide for adjusting the boiler flow temperature.
However, Mike Storey, insulation expert at UK Flat Roofing, adds that without proper insulation, any adjustments to boiler flow temperature will have limited impact, as heat will still escape through the roof, walls, floors, and windows. Lowering the boiler flow temperature should be combined with effective home insulation to maximize energy savings.
When adjusting the flow temperature, it's important to do so gradually and monitor the home's comfort. A lower flow temperature will mean your home takes slightly longer to heat up, but the efficiency gains are well worth the wait, provided your home is well-insulated.
For modern, well-insulated homes, you can go as low as 45°C during spring and summer, increasing to between 50°C and 55°C in winter. Mike Storey is passionate about helping homeowners reduce their energy bills. Insulation is the foundation of energy efficiency, as emphasized by Mike Storey.
Combi boilers are the only type of boilers where the flow temperature can be safely adjusted. Mike Storey, with over a decade of experience at UK Flat Roofing, specializes in providing expert roofing and insulation solutions since 2014.
Lowering the boiler flow temperature can make your boiler more efficient, especially during milder weather, while keeping your house warm. Insulation is often the most effective way to reduce energy costs and should be the first step before fine-tuning heating settings.
- John Small recommends aiming for around 55°C in warmer months and closer to 60°C in the winter for older homes with less insulation.
- Lowering the boiler flow temperature could save the average household around £65 a year, as explained by John Small, but Mike Storey adds that without proper insulation, any adjustments will have limited impact.
- Insulation is the foundation of energy efficiency, according to Mike Storey, and should be the first step before fine-tuning heating settings.
- Combi boilers are the only type of boilers where the flow temperature can be safely adjusted, as Mike Storey, an expert with over a decade of experience at UK Flat Roofing, specializes in providing roofing and insulation solutions.
- During milder weather, lowering the boiler flow temperature can make your boiler more efficient while keeping your house warm, but it's important to do so gradually and monitor the home's comfort.
