Should You Turn Your Boiler off at Night?
It’s a question many people have asked over time, should you turn your boiler off at night time?
Do I need to switch my Boiler off then at night?
The common perception is that in the depths of winter, when you are all warm and cosy in your bed at night, there is a strong chance that you will be comfortably warm. In a modern ish house, with good insulation, double glazing and curtains, the house will usually retain enough heat to be comfortable for a good few hours after lights out. The same for summertime.
There are, as you may be aware, different types of boilers. System boiler, conventional boiler, combi boiler, condensing combi boiler, condensing system boiler or condensing conventional boiler being the main ones.
Newer Condensing Boiler?
Condensing boilers are a lot more efficient because they recycle the heat from the burner exhaust fumes back into the heating system to add to the water temperature. This is similar to how a turbo on a car engine recycles the heat from the exhaust gas to take more energy out. It is a very efficient system; or as efficient as a burning process can be (not that efficient in reality). Also pumps on modern boilers are modulating, so they can pulse on and off when the system needs flow or is up to temperature.
This is primarily because condensing boilers work much more efficiently at lower flow temperatures.
Why might your boiler work during the night?
The condensing part just means your boiler is modern technology but generally it also means that the boiler may have some kind of auto run setting built into the control unit. This could in certain cases mean the boiler fires up on its own during the night; for various reasons.
Reason 1 for boiler coming on
Would be if you have a combi boiler, and sometimes the boiler will fire to pre heat the DHW (hot water) circuit so that you don’t have to wait as long for hot water at the next use of a tap.
Reason 2 for boiler coming on
Would be if your combi boiler has a setting called PRE HEAT, which is for the same function as Reason 1
Reason 3 for boiler coming on
Would be if your boiler system decides to cycle the heating water circuit or heat the water if the system detects the house temperature is falling below the minimum setting (commonly this is 14 degrees if a hive or nest thermostat or similar is in use)
Reason 4 for boiler coming on
Could be if you have a conventional or system boiler and (if its condensing) it does the function in Reason 3, or if the Hot water cylinder has a minimum temperature set and the boiler fires to maintain a temperature above that.
Back to the practicalities
For most people, the dishwasher, washing machine and shower (if its electric) heat the water on demand, and your kettle only needs cold water. So apart from the 30 -60 minute wait for all the radiators to get hot (depending on system size) do you really need to leave the boiler with the option to run overnight?
The negatives to turning your boiler off overnight
Are you well insulated?
A few things to consider include how well insulated is your home? If you have cavity wall insulation, double or triple glazed windows, modern loft insulation, and efficient sealing around your doors, then your house should retain some heat for at least a couple of hours after the heating switches off (after that for all but the most modern and eco friendly house, it’s a rapid loss of heat)
If you don’t have the good insulation factors identified above, then your house is likely to lose heat rapidly when the heating goes off. This can mean damp walls when water vapour condenses on them which also adds to heat loss, but can also create cosmetic damage (or worse) that could have costs involved down the line. With more extreme cold weather conditions, frozen pipes can be a high-risk issue; again this is usually if they are not correctly lagged and located somewhere that is prone to getting very cold (like a loft).
Raising your house temperature
Another factor is that you need to raise the properties temperature all over again in the morning to a more comfortable 21 or so degrees. In the average house your downstairs hall temperature (assuming your thermostat is located there) could be 16 or 17 degrees or less on a winter morning before the heating comes on. Depending on the size of your house , the houses energy rating and the size of the house/boiler/system the time taken to raise the temperate from this level to 21 degrees can be significant (especially with the current cost of gas).
Is it cheaper to leave my boiler on all night?
That’s not to say that it will be less expensive to leave your boiler on, or that you would use less gas because these statements would likely not be true. However, you may well not be saving as much money as you think you are, because of the extra energy used the next day to try and raise the temperature of the house back to 21 degrees (or whatever your chosen temperature is).
If your query pertains to wanting to actually turn your boiler off at the mains power overnight, the answer is no, absolutely do not do this.
The choice is do you have the thermostat set so that the boiler may come on during the night, or not!
How to use your thermostat or heating programmer properly
You can switch your boiler off at night without physically turning its switch off! Particularly with modern thermostats and programmers. You can use one of the following methods.
Thermostat
You can set your thermostat to your chosen minimum temperature before you go to sleep if you want to ensure the heating doesn’t come on. To do this set the temperature as low as it will go, and the heating will not fire up unless the temperature drops massively. For a dial thermostat this may be around 5 degrees, and digital stats usually go lower.
The other option is just to set the thermostat to a low mid-range, like 13 degrees C. In most cases it will not cause the heating to come on, but it will do on very cold nights which can protect your house from the hazards listed above, and will balance on cost pretty much with having to run the heating for much longer the following day.
Programmer
If you have a separate programmer and thermostat then you can change the programmed times on the actual programmer and set the heating to be OFF at for example 10:30 pm at night and come on at 7am every day. (maybe 8am on weekends). The programmer will not allow the heating to come on even if the thermostat is calling for heat (unless you have the programmer set to ON and use the thermostat dial to decide when the heating comes on and goes off).
For a modern integrated programmer/thermostat like a NEST you can set it to ECO mode or turn the temperature dial right down (anti clockwise) to ensure the boiler doesn’t come on. One other factor is the Anti Legionella setting on thermostats like Nests, which brings the boiler on at any time it needs to, to maintain a Hot Water cylinder of 60 degrees at least once a day to prevent legionella bacteria being formed. It is not advisable to adjust this setting.
Pre heat setting
Programmer or thermostat will not affect a pre heat setting on a modern boiler like Vaillant Pro range model. You may hear the boiler fire up now and then, when the heating is off and no hot water is in use. This is to maintain some heat in the DHW (domestic hot water) heat exchanger so that your hot water to the tap is much faster. Having pre heat off means your boiler wont fire at random times but you may have to wait 30 seconds to a minute for hot water at the tap when the boiler has not been used overnight. Having said that our advice is not to use pre heat, as if your pipe runs (length of the hot water pipes around the house) are long from boiler to hot tap, then you will be waiting a while anyway as the tap has to expel the cold water from the pipes before the warmer water can reach the outlet.
Immersion Heater
One option that you have to save gas IF you get a good night electricity tariff and IF you have a hot water cylinder with an immersion heater is to use a timer for it to heat the hot water to temperature during the night. An immersion heater is essentially like a large kettle element that will literally heat up the water in the cylinder. This would mean you would not have to use the boiler to heat the hot water cylinder, apart from maybe a quick reheat if needed during the day. Speak to a qualified gas safe engineer about this option.
