What is boiler flow temperature and how do you change it to save money on your heating bills?
Getting your boiler settings just right is not only optimal for reasons of health and comfort but it can also save you money.
In these trying times, many households are seeking ways of reducing their expenses where possible.
So, how does this apply to boiler flow temperature and how can you adjust yours?
Let’s explore!
What is Boiler Flow Temperature?
The flow temperature is the temperature that your boiler heats the hot water to before circulating it through your system for use elsewhere.
This hot water will be distributed via pipework; some of it (or all of it in the case of a heat-only boiler) would head straight for the radiators, like how spicy food hits on a Friday night.
The rest would make its way to other facilities in your household where hot water is used directly, such as the shower and kitchen sink.
Ideal Boiler Flow Temperature Settings
So, what is the optimal flow temperature?
Generally, your boiler’s flow temperature should be between 60°C and 70°C.
If you were to set it to a higher temperature, it runs the risk of scalding with the water being too hot for use.
Beyond that, it would make your boiler less efficient.
On the other hand, a flow temperature under 50°C is not safe for showering as it increases the risk that Legionella could grow which can ultimately result in Legionnaires disease. Yes, it is a real disease. No, we're not going to explain it more.
Flow Temperature for Vulnerable People
You should also note that the best boiler flow temperature is for those who are young, elderly, or unwell or those people who are so cold year round they're wearing hoodies in July.
In these cases, it is not worth lowering your temperature to (what would otherwise be) the lowest safest temperatures.
This is because it would run the risk of making you unwell or worsening your current state if you are already unwell.
Of course, the above points would also relate to the temperature you set on your thermostat and your showering temperature.
Here are official recommendations as taken from organizations such as the Energy Saving Trust, the World Health Organization (WHO), and the Chartered Institute of Plumbing and Heating Engineering.
| Ideal Temp for heating | Ideal Temp for hot water |
Most People | 18°C | 37°C to 38°C |
Babies/infants | 16 to 20°C | 36°C (should NOT exceed 37°C) |
Children | 20°C | 37°C to 38°C |
The Elderly | 20°C | 36°C to 38°C |
Unwell Individuals | 20°C | 37°C to 38°C ^ |
Pregnant Women | - | 37°C |
*Health warning for newborns: A baby’s room should have a temperature of 16°C to 20°C. Making sure you get this right is critical for their health. This is due to the fact that the risk of sudden infant death syndrome (SIDS) increases if a newborn baby is too hot.
Alternatively, if you are under the weather, you could consider having a lukewarm bath of 27°C to 32°C.
Turning down your boiler flow temperature could also save you up to 8% on your heating bill, check our new guide on whether to turn the radiators off in unused rooms for another quick and free energy-saving hack.
Lowering your Flow Temperature to Save Money
While a range of 60°C and 70°C for your boiler’s flow temperature is the optimal range in general, setting the flow temperature to 60°C is the best for efficiency in most households.
However, if you have a well-insulated modern home, your optimal flow temperature would actually be 50°C.
If you’re unsure as to just how well-insulated your home is, check the energy efficiency rating for your property or check with a professional.
If all else fails, the icicles forming on your nostrils at night can also be used as an indicator.
For most of this article, we will discuss optimal temperature ratings for the average household. If your household isn't average, congratulations. We're proud of you.
If you have a well-insulated home and you see us mention 60°C, replace it with 50°C in your mind, although for lower temperatures, even a well-insulated property should not see its flow temperature drop below 45°. So don't start feeling all too posh.
So don’t turn 50°C to 40°C in your mind. This is true even if regular households may (in warmer parts of the year) get away with a flow temperature of 50°C on occasion.
Of course, naturally, the more efficient your boiler is, the less costly it will be to run. In other words, if your boiler’s current flow temperature is 65°C or 70°C (again returning to recommendations for the average household), lowering it to 60°C should save you money on your heating bills as well as give you something to brag about to your neighbours.
All in all, reducing your boiler’s flow temperature by somewhere in the region of 5-10°C should reduce your gas bills by several per cent.
Therefore, it may interest you to lower the flow temperature further to just 55°C in the spring and autumn.
Please note that you should not confuse flow temperature with direct hot water temperature. That's for amateurs.
For instance, your shower will have its own temperature settings.
In most cases, you should shower at a temperature between 37°C and 38°C, however, this can vary a little from person to person and can be heavily dependent on your need for Scottish showers in the morning.
Related boiler guides:
How to Change Your Boiler’s Flow Temperature
The exact steps required to adjust the flow temperature of a boiler will vary from model to model and brand to brand, so don't come for us if yours is different.
Therefore, you should always check the manufacturer’s manual to find the exact steps required and help us keep the lawyers away.
In this section, we are looking at a broad overview of what this tends to involve.
Of course, even the broad steps will vary depending on the type of boiler you have.
Learn how you can save money by trading in your old boiler for a new, efficient model in our YouTube video below:
Boiler Settings to Change By Type
Boilers with Dials
Your boiler may come with one or two dials that can be used to adjust temperatures. More than likely it will have two. If it only has one, you may want to better review your life choices.
One of these will be designed for changing the heating temperature and will probably have a small radiator icon above it, lest you confuse it with another home appliance.
On the other hand, the second dial will be for hot water and should have a tap icon above. Of course, if in any doubt, double check the manual as how the boiler’s function can vary quite a bit. Again.
So, let’s say you’ve found the hot water dial on your boiler. You may need to turn the dial to the halfway point (or thereabouts) and set the temperature to 60°C.
The manual should explain precisely where different temperature points can be found.
For instance, some boilers will come with various numbers on the dial that signify a certain temperature.
Boiler Dials and Digital Displays
Certain modern boilers utilize dials and digital displays, which can make adjusting your boiler flow temperature a little easier.
This is because a digital display would be used to show the flow temperature.
With this boiler design, you’ll be able to adjust the temperature flow dial and see how you are changing it by looking at the digital display.
Continue adjusting until you reach 60°C or whichever temperature you want to set it to.
Digital Displays with Buttons
For those with a particularly modern boiler, you may find that it has no dials whatsoever. Marty McFly would be seriously impressed.
Instead, some new boilers come with digital displays and up/down buttons. These buttons will feature a + and - symbol, respectively.
As you can imagine, you could simply press the minus flow temperature button to reduce it and watch the temperature drop on the digital display faster than your bank account during the holidays.
In certain cases, you’ll have to hold down the menu button to get to the flow temperature setting in the first place.
Otherwise, the + and - may do nothing or adjust to another setting. In other words, these symbols/buttons serve multiple purposes.
Again, that’s just another reason to always check the manual before proceeding to ensure you get it right. But all in all, it should be relatively straightforward.
Ideal Flow Temperature by Month
As mentioned, in most cases, the flow temperature should be set to 60°C for the average household, while modern well-insulated properties could manage with 50°C.
Here are the best flow temperatures by the time of the year for both types of household:
Time of the Year | Older Homes | Modern Homes |
Jan to Feb | 60°C to 65°C | 55°C |
Mar | 60°C | 50°C |
Apr to Oct | 55°C | 45°C |
Dec | 60°C | 50°C |
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