Lower The Flow Temperature On Your Boiler To Save ££

A recent study by Nesta* found that households can save around 9% in gas just by dialling down the heating flow temperature on their condensing combi boiler. To be clear, this is not turning down your thermostat.

Nearly all combi boilers are not optimised to run as efficiently as they should, which increases household gas bills and emits more carbon. Reducing the operating temperature for heating will help your boiler run more efficiently without reducing your comfort. We help you check if you have the right sort of boiler and show you how to make this simple change. (NB turning down your heating flow temperature is separate to setting your hot water temperature, but we cover that too - see section 11.)

Video and illustrated leaflet now available: if you prefer to watch a video or request a free PDF leaflet that you can print off and/or email to others you can do so via our dedicated Mission page, where you can also find other ways of optimising your combi boiler to reduce your gas bills further.

Contents

1. What does 'turning down the flow temperature' mean?
2. What type of boiler do I need?
3. How do I reduce the flow temperature?
4. What is the correct condensing boiler temperature setting?
5. Can I use trial and error?
6. Will I notice any changes in my heating system?
7. What if I have a health condition?
8. Where can I get more help with this?
9. Why have I not been advised about this before?
10. Is there anything else I can do to improve efficiency?
11. What temperature should my combi be set at for hot water?
12. I have a hot water cylinder, what do I do?
13. Test if you are ready for a heat pump

1) What does 'turning down the flow temperature' mean?

The 'flow temperature' is the temperature your boiler heats up the water to before sending it off to your radiators. Most gas boilers are set up to operate at what is called 80/60 flow and return temperatures. This means the boiler heats up the water (called ‘the flow’) to 80°C. The water returns to the boiler after travelling around all your radiators (called ‘the return’) at 60°C, having given off 20°C to the room.

However 80/60 flow and return temperatures are too high for a condensing gas boiler to achieve the A-rated efficiencies shown 'on-the-box'. It is a little know fact that modern boilers have a variable efficiency between A-E, in other words they are not A-rated out of the box. Studies have found most to be C-E-Rated in the home, equivalent to just 75-85% efficiency.

Your installer should have reduced the flow temperature to give the boiler a chance to run in what is known as 'condensing mode' as much as possible. This is when it can recover the heat that was previously lost through the flue on old style boilers.

At 70/50°C the boiler will start to operate in condensing mode. Only when the flow temperature is 60°C or lower will the boiler recover enough heat to reach its higher efficiency potential.

2) What type of boiler do I need?

You will need to have a condensing combi boiler, i.e. a boiler that produces your heating and hot water. You will have a combi boiler if you do not have a hot water cylinder. It will definitely be a condensing boiler if it was fitted in the last 16 years. A condensing boiler will also have a white plastic pipe underneath the boiler (although it can be grey or black).

What if I have a hot water cylinder? Advice is different for boilers that work with a hot water cylinder. See section 12 below.

3) How do I reduce the flow temperature?

You need to go to the controls on front of your boiler. To be clear this is not your room thermostat, this sets the flow temperature for the boiler. The way in which you adjust the flow temperature and the display information available varies a great deal. Three common are examples are given below: