Save on your gas bills with one simple step | Boiler Flow Temperature

Did you know that you could save nearly enough for a weekly food shop by changing one setting on your condensing combi boiler?

Extensive research by Nesta, the UK’s innovation agency for social good, has found that most homes in the UK can make this change and by doing so save money on your heating bills and lower your carbon footprint.

As part of dwellow's mission to make energy savings simple, in this post we're going to show you how you can turn down your combi boiler radiator temperature (or flow temperature) in less than five minutes.

If you're one of those people that just wants to give it a go - we've built a step by step digital tool which will guide you through the steps to adjust your flow temperature now whilst you're stood right in front of your combi boiler! It's free - so give it a go!

For those that want to know a bit of the detail on heating systems and your boiler flow temperature, read on...

What is flow temperature?

Really simply put flow temperature is the temperature your boiler heats water to before circulating it around your radiators (or underfloor heating). As that water travels round your heating system it typically loses about 20°C and then when it gets back to your boiler it is heated back up to the flow temperature.

Getting this set correctly is critical to ensuring you have good boiler efficiency.

If we go back 25 years boilers were really inefficient boxes on your wall, under a counter or even behind your fireplace (for those of you that can remember the good old back boiler like my granny had!). But technology moves on and in 2005 a new type of modern boiler was mandated in the UK. This is when flow temperatures became important for ensuring optimum efficiency.

These modern boilers are called condensing boilers. They are much more efficient than the old style heating system because they are able to reuse energy that would of otherwise been lost in those plumes of gases that you see coming out of your boiler flue on a cold winters day.

However there is one catch and the reason for this article! To get this condensing to work, the key bit to good boiler efficiency, the water that gets back to your boiler (you might hear it called return temperature) has to be below 54°C - and in reality the lower the better. So if your boiler's flow temperature is set at 75-80°C its not working at its maximum efficiency.

What's worse is your combi boiler probably switches itself on and off a lot (called cycling) which increases wear and tear. Meaning more break downs, cold showers and the cost of calling out an engineer to fix it.

So let's give your combi boiler a tune up!

How much could I save?

What Nesta found was households could save about 9% on their gas bills, assuming their flow temperature was set at 80°C.

So what's that in pounds and pennies?

A medium-sized household with an annual gas consumption of 12,000 kWh this works out at an annual saving of around £65 (based on gas prices in September 2023).

So not a massive amount of money to some people but its enough for a weekly food shop and you'll also be reducing your carbon footprint. All for 5 minutes effort using our free flow temperature tool here.

But everyone's home and heating system is different. If you don't know your annual gas consumption - we've got a tool for that! Give our home plan a try (it's free as well) and we'll give you a pretty good estimate of what you probably use today. You can try it here.

How do I tell if I have a condensing combi boiler?

If you have one, you're in good company as it's the the most common type of gas boiler in British homes today. The way you can tell if your heating system has one is really simple.

1. Do you have a hot water cylinder? If not then you've got a combi boiler - this basically means the boiler heats hot water as and when you need it rather than storing a tank full of water
2. Was you boiler fitted in the last 15 years? Then if it was it will definitely be a condensing boiler - but you can double check as it will also have a white plastic pipe coming out from underneath the boiler.

What is the correct condensing boiler temperature setting?

A flow temperature of 60°C or below means your combi boiler will be in condensing mode (meaning the temperature of the water that returns to your boiler will be around 40-45°C).

When your combi boiler is in condensing mode it will recover heat that would otherwise be lost so that it runs more efficiently. Unlocking for you those lovely cash savings!

Will this change how warm my home is?

No, but you will probably notice that your radiators don't feel as hot. This is because the water circulating around them is cooler, which is the whole point of this change. At this new lower flow temperature of 60°C your home should still feel warm whilst you coin in the savings.  

The other change you may notice is it will probably take your home a little longer to heat up. Because most of us have our boiler's flow temperature set so high we have got used to really short heat up times. So if you have your heating set on a programmer it may need a little longer to get you up to your preferred temperature.

Will my hot water be cold?

No don't worry - changing the flow temperature won't effect your hot water temperature - so no risk of a cold shower!

Can I really do this myself?

Yes. You may be worried about changing your boiler settings but it really can be done by anyone, including you. In fact boiler manufacturers and your energy company actually recommend this change as a way to lower your energy bills.

It really is a quick change and shouldn't take you more than five minutes - we explain the steps next or use our online flow temperature tool here.

And remember these changes are not permanent - they are easy to change back to a higher temperature or even back to the original temperature settings.

The three steps to a more efficient heating system

Step 1: Find your boiler!

To make the changes you’ll need to be in front of your combi boiler not your room thermostat.

The controls you need will probably be on the front of your combi boiler, and may be behind a flap. Just in case you want to go back to your old settings you could take a photo of your controls now.

Or if you use our digital flow temperature tool we'll even save these for you (remember its free and you can find it here.

Step 2: Look for the radiator symbol on your controls

The radiator symbol shows you which control manages your central heating flow temperature. Different manufacturers have slightly different symbols but they should look something like this.

Your combi boiler will have this symbol next to one of its dials or on one of its buttons.

Step 3a: Adjusting the boiler flow temperature (if you have a dial)

Most combi boilers don’t have the temperature displayed around the radiator temperature dial. You’ll want to adjust the target radiator temperature to about 60°C.

If your combi boiler does not have a digital display, you won’t be able to tell the exact radiator temperature. If you have a dial turn the dial to roughly 12 o'clock.

If your radiator temperature is already below 60°C, we recommend that you keep it at the current temperature setting.

Step 3b: Adjusting the heating flow temperature (if you have a digital display)

First, press the button with the radiator symbol on or near it. This should change the display to show the current radiator temperature.

Next, use down or minus buttons to set the radiator temperature to 60°C. The images here show how this might look.

If your radiator temperature is already below 60°C, we recommend that you keep it at the current temperature.

What to do if your home is too cold after making the change?

After changing your flow temperature, you may notice your radiators being warm rather than hot to the touch – this is normal and a sign you've changed your boiler flow temperature. Many people don’t notice any other changes to their comfort.

If you find your rooms are taking too long to heat up, or not getting as warm as you’d like, try increasing the temperature again by 5°C.

How long should I extend the time I have my heating on?

If you switch your heating system off at night, you should try setting the heating to come on 15-30 minutes earlier. By doing this you are allowing a more gradual warm-up time before your home achieves your desired temperature. As your heating system is operating more efficiently this should not increase your heating bills.

Can I turn my boiler flow temperature lower than 60°C?

Yes. If after making the change your home is still cozy then try turning the boiler flow temperature down by a another 5°C. You'll save even more on your heating bill and carbon footprint.

Can I change the flow temperature at different times of the year?

Yes - that's a good idea. You can change the flow temperature for example during really cold weather you can turn the flow temperature up, but don't forget to reduce it again after.

What if someone living in the house is vulnerable or has a long-term health condition?

Staying warm is very important and we wouldn't want your well being to be put at risk. So if you or someone you live with has a long-term health condition we wouldn't recommend you make this change.

I have a hot water cylinder, why should I not change the flow temperature?

If you have a hot water cylinder you'll have what's called either a heat only or system boiler. Most of these types of gas boilers don't let you choose a radiator flow temperature that's different from the hot water temperature without changing how the system is plumbed together.

This causes a problem as when you store hot water in a hot water cylinder, is needs to be hot. This is because hot water stored below 60°C risks the development of Legionella bacteria which grows in stored water.

To keep you save we don't recommend changing the flow temperature without asking an engineer first.

It's different for combi boilers  as they let you set a different temperature for the radiator heating temperature and hot water. They also don't store water, heating water as an when you turn on your hot water taps.

So if you have a combi boiler, contamination is much less likely.

How are boiler controls different to central heating controls? 

Simply put central heating controls like your room thermostat, programmer and radiator valves turn your heating on and off, whilst the controls on your boiler (which we've just shown you how to adjust) change the temperature of the water in your system.  

When should I call a boiler engineer?

If you struggle to follow any of these steps maybe ask a family member or friend. Or when you next have your boiler serviced you should ask the engineer to check the flow temperature for you.

When to Call a Gas Engineer

Maintaining a boiler is crucial for both safety and efficiency. Knowing when to call a gas engineer will help ensure your boiler operates at peak performance and prevent potential hazards. 

There will be times though when you should call an engineer - for example if your boiler is frequently turning on and off, you hear unusual noises or if the boiler is leaking. These can all lead to inefficient heating and increased energy bills. It's important to keep an eye on your heating system.

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