Is it cheaper to leave your heating on all the time or turn it on and off?
Having advised thousands of homes on how to become more energy efficient and reduce energy bills there is one question we hear time and time again:
‘Is it cheaper for me to leave my heating on constantly 24/7 (with the temperature controlled by the thermostat) or set it via the programmer to come on at certain times?’
The answer is – it depends!
By leaving your heating on, the boiler will have to work to keep the temperature at a set level, whereas having it come on and off at set times will only heat your home at a given period; however your boiler will need to work harder to heat the house from cold to the required temperature.
Is your home well-insulated?
The answer is purely dependent on how well insulated your home is. If you’re home is very well insulated, you are better off leaving the heating on at a set temperature, where the thermostat will work with the boiler to maintain the temperature relatively easily, since there is little heat loss occurring.
Conversely, if your home is not energy efficient, potentially a Victorian property for example, then you are better off just heating it up for the times when you need it. The majority of people are out during the day, so most people opting for this heating schedule will fire the boiler to come up early in the morning for a couple of hours so the house is nice and comfortable when they wake up, then set it to come on in the late afternoon until they go to bed.
It will be more cost effective to heat the home as and when you need it, as any heat you generate will be lost fairly quickly through the walls, so if you try and maintain that warmer temperature all the time, your boiler is going to have work incredibly hard. This does mean that you are not going to have the home ‘warm’ all the time, but if you work during the day, it should make things a lot cheaper compared to leaving the boiler on.
Don’t take our word for it – test it for yourself!
So granted I have cast everyone into two baskets – energy efficient and not energy efficient. The truth of the matter is that you will most likely be somewhere between the two, so which heating method will work for you?
Well there is a simple test you can run at home to see whether you should have the heating on all the time or you should use the programmer so it only fires up a couple of times a day. Basically over the course of two weeks – test each method. You will need to take gas readings to do the test, and also bear in mind that if a sudden cold spell hits then your results will most likely be null and void!
The importance of insulation
We seem to touch on this a lot, but it really is a fundamental truth. If you live in a well-insulated house you will spend less on your energy bills.
In terms of cost-effectiveness, loft insulation is the cheapest and easiest to do, costing about £250 if you opt for mineral wool insulation. This will pay back in just a couple of years. Cavity wall insulation and floor insulation are the next things to target.
If you live in an older solid wall property, cavity wall insulation won’t be possible and you will need to insulate either internally or externally.
Getting a more efficient boiler can also help lower your bills, along with better heating controls. For example, if you don’t have a thermostat, you will likely be overheating your home when the programmer kicks in. Thermostatic valves on your radiators can also regulate the temperature in rooms and they allow you to stop heating rooms you aren’t currently using.
Think we missed something? Do you have a different opinion?
Comment below to get your voice heard…
I have always wondered about this, I have an old victorian property that has very little insulation, in fact I am looking to install triple glazing. But now I know – turn it off when I am not there! Thanks for this, really useful.
I too have a very cold house, im wanting to get the loft insulated, being quoted 6000, i had no idea its so expensive. Everyone was telling me its free with a grant.. 😭
This logic, I’ve found through experience, is flawed! My house has solid walls so doesn’t retain heat as well. The thing is, this means that when the heating is off the house gets colder then an insulated house and so the boiler runs for a longer period to get back up to temp.
To keep my house at 20’c the boiler runs for about an 8hr period in total over 24hr. To get my house back up to 20’c from the 15’c it drops to over night takes in itself at least a 2hr constant run. Double this for the evening warmth and you’ve got at least 4hr of a 14hr heat period just for getting back to 20’c period. The other 4 are then used maintaining 20’c for the periods heat is required.
I know this for a fact in my own house, and I can see on hive and can see both approaches.
Just a FYI for you and others.
Completely wrong ! all the time you are maintaining the rooms at (say) 25c – you are losing heat through the walls at a rate prescribed by the temperature difference across the walls. Allow that room temp to lower overnight – lessens the heat loss. THAT IS THERMODYNAMICS.
This!
Genius, turn it off when you are not in
I love the Internet. I have always argued with my wife over this one and it turns out I am right! Really useful article and one that I shall definitely be showing the wife!
LMAO
chauvanist.
Nine out of ten people who argue that you should leave the thermostat set at one temperature all the time just don’t like the cold. I love sleeping in a cold room at night so I turn the heat off at night.
When I lived in an old house with an oil system, I saved nearly a 1000$ one year leaving it on at 19 C all the time. Then, the next year, I had this idiot downstairs neighbor opening her windows at -30C, the floor would turn icy… I moved cause of that imbecile. I found out raising or heating after lowering for a while cost a bundle. Never again and will I rent something heated by oil or gas.
This answer is misleading because it is always better to have the heating on only when you need it (when you are in the property), irrespective of the level of insulation. The short answer is to keep the temperature as low as you can bear (without being uncomfortable) and turn it off when you don’t need it, for example if you are out, or in bed.
The correct technical explanation is simple physics (thermodynamics) and that is that the heat lost is proportional to the temperature difference between the external and internal temperatures – the bigger the difference, the more heat is lost. A well insulated property will lose less heat than a poorly insulated one, so for any given internal and external temperatures, the energy consumed (and therefore the costs) will be lower. Leaving the heating on when it’s not needed maintains a higher temperature difference (because the internal temperature does not fall), so more energy is wasted, even though the heating may have to work harder when it’s switched back on.
Sorry daveM but that is only half the picture and not reflective of real life. Your assessment is a paper exercise and is flawed. Heat loss of a property is not the same as energy consumption. By using the top up method you will find it brings more boilers into the condensing mode when improperly configured with too high flow temps (as most are because plumbers don’t have time to properly balance rads and find optimal flow temps so they set a 75c or 80c flow temp and leave). Letting temps go down and then doing longer boiler burns results in increased return temps and less efficiency by reduced condensing in these systems. Doing “top up” burns results in colder return temps since the boiler does more shorter burns and effectively is on just enough to exchange the water in the rads before then turning off again. So in more insulted homes, you will find that your efficiency gains via leaving the heating ticking over negate the fact that you lose more energy via higher avg temp. This is why it can be just as cost effective to leave the heating on.
Wow, some rather rude and arrogant people here pushing their ‘expertise’ or opinions! I agree with you, Dave and a couple others here.
I live in a spacious, semi-modern apartment on the 2nd floor. There are 4 apartments here only. I work from home and like to be comfortably warm but not stuffy. Since over a year ago I started keeping my boiler on constantly, set to the lowest temp it would go and boosting for a while if the outside temp suddenly dropped. When I used the timer. I used to set the boiler thermostat to the highest setting and if it was really cold outside and I’d been out all day, it would take hours before the place felt comfortably warm. Since keeping the boiler on constant, my gas bills have dropped. The radiators are not hot to the touch on the lowest boiler temp setting and the pipes are warm and yes, I like it if I have to get up in the night that it’s not cold!
As my flat is modern, reasonably well insulated, and I’m home a lot, it is cheaper and preferable to keep the boiler running on constant/standby. I even left it on when I was away for a week. It just took the chill off and kept my houseplants alive although with me not living in the apartment, did feel cool when I first walked in, so obviously normal domestic activity and habitation in the home generates more heat. I now never have to turn the boiler up full blast as I did when I used the timer, even if the outside temp is freezing.
So in MY case, constant and low is the clear winner. Every home is different and factors like how insulated and energy efficient your home is, the type of property it is, its geographical location, its age, the direction of your main living area, the windows and surface area they take up, what activities you do, what appliances you have running that generate some heat, the efficiency of your CH system, individual radiator thermostats, the number of people living there and how long the home is occupied in the day and of course personal preference (etc) all contribute to what system is cheapest.
In fact, my monthly direct debit had just been reduced again, although the energy supply contract I have is coming to an end so unavoidably I’ll be paying more every month with the massive gas price increases. 😕
Great response!
When he says ‘on’ he doesn’t mean constantly running. On means ‘standby’ its thermostatically controlled. My UFH is ‘on’ all day while I’m at work but because the house is insulated well the ufh never actually runs. The only thing I don’t let come on anytime is the domestic hot water. I’ve a night rate electricity meter so the hot water only reheats after 11pm. Saves a couple of cents.
I have an air to water heat pump so it’s all very efficient regardless of the time of use. We are saving close to a grand a year compared to oil central heating even if we leave windows and doors open too long etc.
Well done Dave. We have this argument with UFH providers all the time; “just leave it ticking over it uses less energy”, is the same as leaving your car running on the drive overnight during winter to keep the windscreen clear of frost. I prefer to go outside, start the car and come back in for a cup of tea. 5 minutes later car is warm, screen is clear & I’m ready to roll. to work. Common sens really
I disagree Martin, this is very property dependant.
A car has an extremely low thermal mass so the heat leaves it immediately. Fortunately ICEs give off an immense amount of heat as a waste byproduct.
My house for example has large solid stone wall. The thermal mass of these is charged with heat which means if the heat is maintained, the boiler has to work less hard. If I let them get cold then a lot of heat energy and time goes into recharging these. I appreciate this isn’t the case for well insulated properties but properties like mine are not suitable for insulation
Spot on
The right answer from someone who understands the science. It really is that simple, no debate, daveM is correct 🙂
Good to see someone here actually understands the science of this, rather than passing off opinion as fact.
Of course that is correct – people should only turn their heating on when it is required, however most people aren’t doing this – we come across a huge number of people who use their thermostat to manage their heating. This is what most people do, it means they don’t need to be ‘on it’ since their thermostat won’t overheat their homes. The issue is that if you live in an older property which lacks insulation then you will burn through fuel – so turning it on and off with a programmer is better. Conversely if you live in a really well insulated house, then leaving your heating on all the time (but using the thermostat to manage the temperature) is the best way to go.
James I agree with you.i typed a lengthy reply but mistakenly addressed it to Dave, but it was meant to be to you! I don’t agree with what Dave said. It’s very late, I can’t sleep tonight and decided to research some things going round in my little head so found this article and the debates and had to join in!
That is nonsense James. You can’t have one principle for one type of house and another for a different type! You are clearly NOT a scientist nor an engineer. Sure, the energy loss/use (it’s the same thing) will be less in a better insulated house, But it will still use/lose more energy the hotter it is, because the hotter it is the faster it loses it (temperature gradient between inside and outside). The energy used to re-heat the house is a red herring. It’s the overall loss/use that dictates what the cost will be.
We had a guy come fix our radiators because it took almost an hour to heat and he had to bleed it out because there was air in it. He suggested we leave our radiators on at a certain temperature and it will be cheaper so we did that of course. A month goes by and we get our gas bill, it came out to be $256!!!! Its not cheap at all to leave it on at all times and we had it set to 62 degrees!!! Do not leave your radiators on!!!
For me it was defintely cheaper to turn my heating on and off, basically because if the house is cold in the morning it forces me out of bed! It bugs the wife and kids, but it then means that our heating comes on at 4 pm, and it tends to warm up pretty quick and it goes off about 10pm. I can’t beleive it would be anymore energy-efficient to keep the heating on all the time?
Hi Orto, it is normally only worth doing when the house is incredibly well insulated (i.e. a new build). The reason here is the rate of heat loss is extremely slow, so the boiler will only turn on to ‘top up’ the heat in the house. When you consider older properties, they get cold very quickly when the heating is switched off, so for these properties it is normally worth trying to minimise cold draughts entering the house (by draught proofing) but actually the heating should only come on as and when it is required to help lower energy usage.
I live on the 19th floor in a high rise believe it or not it can get really cold, but I only put heating and hot water on when needed, I’ve tested always and that’s come well the cheapest for me.
It is NEVER cheaper to let your heating run continuously.
Hi how much would it cost for me to keep a 13fin oil radiator on all day every day it’s 3000w.
Expensive I can assure of that
Hi Kim, if it ran 24/7 it would cost approximately 36 pence per hour (3kw x 12 pence per kWh). To be honest though, they normally have thermostats built in which ensures the heating is not left on all the time, this means you would actually use slightly less. The best thing to do to get an accurate measure of how much electricity that device uses is either use an energy monitor or wait until you have a smart meter installed on your property. Once you get this, you can then see the cost of keeping the unit on over that time. The key to getting an accurate reading though is to ensure that you don’t switch on and off other appliances as you are carrying out the test, as this will obviously impact the amount of energy used too!
Depends on your heating and insulation. With underfloor heating it is better to leave it on AS IT TAKES ALOT OF ENERGY TO HEAT IT UP AGAIN.
NO – heat loss is heat loss, and you lose more when the temperature differential is greatest. You don’t change that principle no matter what insulation you have or what heating you have.
BUT – the less insulation you have – the more your losses, and the more you have to replenish with your heating.
It would take less energy to re heaat than to maintain the temeprate continuously.
But it cannot possibly take more energy than was lost
The one issue not dealt with by most of the posts in this thread is the efficiency of the heating means. You will always have to put more energy out of the radiators or underfloor pipes by running 24/7 but your system might not run as efficiently when working across a big gap between flow and return temperatures if for example using a heat pump with an underfloor system which could mean that you have to put more energy in to get the required amount out when operating across a large temperature range. This is why purpose built heat pump systems work at lower flow temperatures and use larger bore pipes and radiators and why hybrid systems can make sense when retrofitting to a previously installed set of pipes and radiators. Another issue with underfloor/heatpump heating is the time taken to heat up from cold which can mean that it takes longer to get to temperature tempting people to turn on additional heating such as the 3kW oil filled radiator mentioned elsewhere in the thread and this could get very expensive. Generally I agree with the posts suggesting that it is almost certain that timed on off is better than 24/7 running but, like with most things, there may be a few exceptions to prove the rule!
Vilnis, what you say is untrue. We have a passivhaus and for us it is much cheaper to keep the boiler on but use the Heating controls to control it.
Agreed Seb, the level of insulation and how good the heating controls both have a huge impact on whether it is cheaper just to leave your heating on all the time.
Superb web site because it was simple to read and answered ALL the questions I had regarding radiators and heating the home. Excellent. Thank you.
hI GUYS AND GALS,
CAN’T YOU RUN A CONTROLLED EXPERIMENT LIKE THAT YOU SUGGEST AND PUBLISH THE RESULT TO EMPIRICALLY ESTABLISH THE TRUTH (FOR A GIVEN PROPERTY)? pERHAPS DO TWO EXPERIMENTS – ONE IN A NEW BUILD AND ONE IN A VICTORIAN PROPERTY.
jUST A THOUGHT,
rIK
Is it safe to switch a boiler off and on from standby every day?
You kindly recommended Mr Stephen Edwards to me for a boiler service. He is truly remarkable – while working he identified a fault with my three year old Worcester-Bosch Greenstar boiler. This was a potential safety concern; he gave me appropriate advice. He also provided a carbon monoxide alarm. Altogether, in every way, I was greatly impressed. He is a phenomenally hard worker, honest and presentable and works methodically and knowledgeably. He put up with difficult working conditions and parking restrictions without complaint. You were right to recommend him and I’m very glad you did. Finally, a heating engineer whom I feel able to trust.
Hi how much would it cost for me to keep a 13fin oil radiator on all day every day it’s 3000w.
Hi Kim
The amount of electricity used by your heater, assuming no thermostatic control, would be 3000w x 24 hours / 1000 = 72kWh. You will see the cost per kWH, otherwise known as a “Unit”, on your latest electricity bill.
I beg to differ regarding keeping the heating on or switching it off. The sure way to reduce fuel consumption is to reduce the temperature indoors since heat loss is proportional to difference of temperature between indoors and outside. The easy way is to have the heating off at times when that has no effect on comfort e.g. When no one is at home or when everyone is tucked up under their duvets..The classic question is: would you save by leaving the heating on if you were going away for a week or more?
I agree completely with daveM. I.e. You save by switching off. This is just A level physics (and I have a Cambridge PhD in the subject). Test question: do you think that if you were going away for a month you would save by keeping the heating running?
I suggest you go back to school since your lack of practical experience is showing. Heat loss of a property is not the same as energy consumption. By using the top up method you will find it brings more boilers into the condensing mode when improperly configured with too high flow temps (as most are because plumbers don’t have time to properly balance rads and find optimal flow temps so they set a 75c or 80c flow temp and leave). Letting temps go down and then doing longer boiler burns results in increased return temps and less efficiency by reduced condensing in these systems. Doing “top up” burns results in colder return temps since the boiler does more shorter burns and effectively is on just enough to exchange the water in the rads before then turning off again. So in more insulted homes, you will find that your efficiency gains via leaving the heating ticking over negate the fact that you lose more energy via higher avg temp. This is why it can be just as cost effective to leave the heating on.
Should you therefore turn the heating off if you pop out for 2 mins to put the bins out?
Of course not you are to rely on the thermostats to regulate and keep the temperature reasonable not manual control as it take time tp heat up and cool down. Its the average temperature that matters Eben if you have electric heating you set the heating with thermostat and or timer and turn up or down if heat build up or lowers too much
Should I leave my immersion heater on all the time I am on economy 7 and just keep 1/2 of the storage tank heated
Hi Carole, when you are on Economy 7, there are normally 2 immersion elements – one linked to the cheaper night time electricity and one linked to the day time (more expensive) electricity. The cheaper to run immersion could be on all night as the thermostat on the hot water tank will stop it producing hot water when the required temperature is met, however we would normally suggest running the ‘cheaper’ immersion a couple of hours per night and only running the day time immersion when there is an absolute emergency for hot water as this will cost you about 3 times as much to produce hot water at this time.
Truly unbelievable greenage! It is irresponsible to publish your view here without referencing scientific research paper to back up that leaving your heating on all the time is cheaper than on/off as required, I’ll go with the scientifically accepted understanding everytime otherwise as should your readers.. I have a swimming pool and cringe everytime a pool man claims it’s cheaper to heat then maintain a hotter operating temp than just heat when needed. An outside pool is relatively poorly insulated, even with a cover on.. The level of insulation makes no difference to what is the cheapest method.. Think about it.
Hi Physics Teacher, I am going to have to disagree. The level of insulation makes a huge difference, especially if the insulation is on the outside of the property (external wall insulation) since the bricks in the property warm up and act as a thermal store. It is clearly also true, if heat loss occurs at a lower rate through the properties envelope (ie. walls, roof and floor) then the amount of heat required to replace the lost heat will be lower.
TLDR: If your insulation is good enough the difference in cost between continuous operation and on-demand operation should be negligible and may well be more convenient but can never be cheaper.
The level of insulation can make a big difference to the “difference” in energy usage between running a system 24hours a day vs just when needed and it can certainly reduce the energy usage per hour of maintaining a particular temperature. It does not, however, change the fact that a building at a temperature above ambient will always be losing some energy to its surroundings and therefore some energy must be introduced to maintain that above ambient temperature.
When a building’s internal temperature is the same as it’s external temperature no energy is being wasted and therefore every hour that the building sits cold (and heat is not required) it is performing at 100% efficiency. When the building’s internal temperature is higher than it’s external temperature some energy will be being lost and the level of insulation only affects the rate at which that energy is lost. The point here is that a building’s efficiency only drops when there is some higher than ambient internal temperature, the rest of the time it’s performing at the maximum possible efficiency.
The more insulation a building has the less time the building spends with its internal temperature being the same as its external temperature. Therefore the difference in cost between running the heating system continuously or as needed decreases as insulation increases.
A building which is very well insulated and cools back towards ambient temperature so slowly that it doesn’t reach the ambient temperature in the time when heat is not required therefore is continuously losing energy at a constant albeit low rate. Therefore the heating system will be no more or less efficient if it is set to be on continuously or only as needed because the building never cools to ambient and so it always has some energy to lose every hour. It would not be possible for continuous operation to become cheaper than only heating when required because that would imply that you are actually creating energy, and as we know it is not possible to create energy.
It may certainly be more convenient to always have the heating turned on and I’ll acknowledge that with some really good insulation the financial cost of running your heating continuously may be very low especially if you have solar panels or some other “free to run” energy gathering systems but it still wouldn’t be cheaper (though it also wouldn’t be any more expensive) than running your heating on demand.
Here are three examples using some hypothetical numbers:
Assumptions:
1. The exterior temperature is 10C (degrees centigrade)
2. A comfortable interior temperature is 15C – 20C
3. The thermostat turns on the heating system when the temperature falls below 15C and turns it off when the temperature reaches 20C
4. We’ll assume no delay in heat being produced and that heat reaching the thermostat (i.e. no overshoot)
5. Numbers may be somewhat unrealistic in order to make the mathematics easier.
6. The temperature drop (energy loss) is linear over time.
7. The heating system increases the temperature by 1C for each kWh used.
8. The occupants get up at 7 am and leave the building at 8 am.
9. The occupants return to the building at 6 pm and go to bed at 10 pm.
10. The occupants only require the building to be at a comfortable temperature when they are awake and in the building.
11. A poorly insulated building’s internal temperature drops by 5C per hour
12. A medium insulated building’s internal temperature drops by 1C per hour
12. A well-insulated building’s internal temperature drops by 0.5C per hour
13. Energy (kWh) can come from multiple sources e.g. gas boiler, solar panel, sun trap, etc and some of these energy sources are cheaper than others.
If the system put on a time clock to be active only during hours of occupancy in a poorly insulated building:
At 7 AM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 8 AM the building has dropped to 15C and the system is turned off
At 9 AM the building dropped back to 10C
At 6 PM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 7 PM the temperature has dropped to 15C and the system uses 5kWh to bring the temperature back to 20C
At 8 PM the temperature has dropped to 15C and the system uses 5kWh to bring the temperature back to 20C
At 9 PM the temperature has dropped to 15C and the system uses 5kWh to bring the temperature back to 20C
At 10 PM the building has dropped to 15C and the system is turned off
At 11 PM the building has dropped back to 10C
Over a 24 hour period, the system would use 35kWh to maintain the temperature
If the system put on a time clock to be active only during hours of occupancy in a medium insulated building:
At 7 AM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 8 AM the building has dropped to 19C and the system is turned off
At 5 PM the building dropped back to 10C
At 6 PM the temperature of the building is 10C and the system uses 10kWh to bring the temperature to 20C
At 10 PM the building has dropped to 16C and the system is turned off
At 4 AM the building has dropped back to 10C
Over a 24 hour period, the system would use 20kWh to maintain the temperature
If the system put on a time clock to be active only during hours of occupancy in a well-insulated building:
At 7 AM the temperature of the building is 13.5C and the system uses 6.5kWh to bring the temperature to 20C
At 8 AM the building has dropped to 19.5C and the system is turned off
At 6 PM the temperature of the building is 14.5C and the system uses 5.5kWh to bring the temperature to 20C
At 10 PM the building has dropped to 18C and the system is turned off
Over a 24 hour period, the system would use 12kWh to maintain the temperature
If the system is active 24 hours in a poorly insulated building:
At the beginning of each hour, the system will use 5kWh to bring the temperature from 15C to 20C and over the course of the hour, the building will drop back to 15C. On average each hour the system will use 5kWh to maintain a comfortable temperature.
Over a 24 hour period, the system would use 120kWh to maintain the temperature
If the system is active 24 hours in a medium insulated building:
Every 5 hours the system will use 5kWh to bring the temperature from 15C to 20C and over the course of 5 hours the temperature will drop back down to 15C. On average each hour the system will use 1kWh to maintain a comfortable temperature.
Over a 24 hour period, the system would use 24kWh to maintain the temperature
If the system is active 24 hours in a well-insulated building:
Every 10 hours the system will use 5kWh to bring the temperature from 15C to 20C and over the course of 10 hours the temperature will drop back down to 15C. On average each hour the system will use 0.5kWh to maintain a comfortable temperature.
Over a 24 hour period, the system would use 12kWh to maintain the temperature
Now I’ll agree that these examples are somewhat simplistic but the principle still holds.
Your assessment is flawed and hasn’t taken into account the fact that a boilers efficiency changes based on its return flow temps. So in situations where you need a large single heat input (eg you have returned home after having it off all day) you may be running at 87% efficiency due to higher return temps. Where as many smaller heat inputs during the day to maintain a temperature may all be running at 97% efficiency since the return flow temps tend to be room temperature more of the time since the boiler fires and its on just about long enough to exchange the water in the rad before turning off again. Return temp is important to be as low as possible to increase condensing in modern boilers. So in a better insulated home you can find the efficiency gains from always on can negate the extra losses from higher average temp of your home.
Someone finally explains this in great detail. DaveM’s response should have been enough but no, people like James, still continue to propagate the lie (yes, it is a LIE!) that given the right circumstances, it could be cheaper to leave your heating turned on 24/7. Absolute nonsense, spouted by an idiot who thinks they are a genius!
No need for that is there, people are only putting forward suggestions
I think some people are confusing efficiency with cost. In my own newbuild home, I find that the boiler works to replace heat infrequently because heat loss is low. Insulation is high.
However if I go out for a week (and I always turn down the stat when I do this) the temperature can drop down as low as 12C before I return – it takes a lot of energy to bring this back up to 20C when I do return.
There are also other factors while the house is occupied. Using cooking appliances particularly can work to increase the ambient temperature of an area, reducing the demand on the boiler from the thermostat.
I am experimenting to find the optimum solution for myself, but it is looking like while I am here regularly (out for 10 hours a during the day working), it is best to maintain a constant temperature, but if I leave for an extended period ( a few days or more), I should turn it down to ‘frost protect’
Perhaps I should add that my thermostats are set to 16 constantly, unless I feel particularly cold when I boost it higher, but I find my gas bills are low.
I find the boiler can spend a good few hours bringing the temperature up from 12 to 16, but only comes on 6 or so times a day for less than an hour in total to maintain the temperature.
I think scientifically it takes more energy to increase a temperature than it does to maintain a temperature…
Something to do with the specific heat capacity of a given substance. It’s a long time since I did school science 🙂
I certainly agree that an older house or a less well insulated one would lose heat at a rate higher than my own, and therefore running the heating constantly may prove costly.
Wooly thinking!
Older type well insulated Homes have solid internal walls, these act as massive thermal stores, in long cold external temperatures keeping the temp buffer stable, therefor continuous heating of a slightly lower than required and boost when the home is occupied ( Stove) is most efficient, stops lots of cycling of central heating systems.
No wonder there’s so much scientific misunderstanding around if even highly educated engineers and scientists can get this wrong (and I know of a few). The idea that using heat now can save on heat later literally goes against the first law of thermodynamics.
The simplest way to explain this is by using a leaky bucket as a metaphor for your house. You can keep it topped up full; you can keep it topped up to a lower level (reducing the rate of loss); or you can let it empty completely (stopping the loss entirely).
If you allow it to empty completely before filling it back up when needed, this simply cannot use more water than keeping it topped up to a low level the entire time.
The amount of insulation is exactly the same as the size of the leak. A smaller leak will lose less water over time but the principle remains the same as a larger leak.
If anyone still thinks that leaving the heating on, or topping the bucket up, will use less energy/water then I’m all ears – but I’ve never seen an explanation of how this would work, other than the non-sequitur that it has cooled down so much that it somehow needs more energy to heat back up again.
Thank you for this explanation. I’ve been reading a lot (of nonsense it turned out) and playing with my settings to experiment with a condenser boiler. I now realise I’ve been on a fools errand. I’ve also been reading about heat pumps and there seems to be a lot of confusion. Apparently they should be left on all the time to maximise efficiency. So is there something else factored into this or is this just plain wrong?
Been there, done it. We had LPG when first married. Our bungalow was over insulated (if there can be such a thing) – we built the property ourselves and put rock wool under the voided floor, hanging the insulation in netting between the floor joists, but still keeping a void, super insulated the loft and used insulated blocks for the inner walls. For a week we put the heating on constant, but at a low temperature and boosted it for an hour when we came home. The following week, in very similar weather conditions, we put the heating on timed – 2 hours am and pm. We took meter readings at the beginning and end of each week and found that leaving it on a low setting constantly was more economical.
Reading the comment to the question of leaving your heating on all the time or not, and the answer “it depends”, and then giving examples I find infuriatingly annoying in maintaining the urban myth of the statement that it is better to leave your heating on all the time. A building in the heating season losses heat at a rate that depends on the difference between inside and outside temperature. Remember your first day in science? Heat goes to cold?
If you heat a house to above the outside temperature you lose heat. It is called heat loss for a reason. That is energy. You have to replace it if you want to maintain the temperature.
Next, when does your boiler operate most efficiently? When it has the coldest return temperature i.e. the house is starting from cold. This is because the boiler then gives back the latent heat component of the flue gas heat and hence you see plumes of condensation coming out your flue.(post 2005 boiler) You get roughly 10% of your gas energy back by condensing all the latent heat.
So. If you are not in the house don’t heat it. If you have an old house, put the thermostat on a reduced temperature to protect the fabric against condensation while you are away especially if unoccupied for a long time.
Never just heat your house because some badly, mis or ill informed/educated comment comes about in a blog, from what your granny or Joe the gas engineer said. Would you keep a kettle boiling all day because you think it will be cheaper than heating it up everytime you want a cuppa? Would you leave your car running overnight so it was nice and toasty for the drive to work in the morning because it is better to keep it hot than warm it up each day? You know you are wrong to all those who continue the myth and to those realising this misguided direction do not follow, stop them with the above simple and accurate statement.
I just read there were a lot more comments on this as I was about to post.
There are obviously still too many people that think they are educated in this state but have no idea of fundamentals.
Really helpful explanations, and also the comment comparing the leaky bucket to poor insulation
Do you have analysis of *electric underfloor heating* as the sole means of heating a well insulated house? I appreciate that electricity is more expensive, but we are considering buying a retirement home (part of a converted stable block) well insulated, but with only electric Underfloor heating. (No figures available for annual running costs)
Thanks for posting about the Energy Efficient Boilers that help to maintain the thermal effect. Its really helpful.
Hello, Thanks for this advice,
Agreed BUT how about if house empty for 2 weeks in winter and heated to about 60/16 degrees? What do you think in that situatiod?
Regards,
Mike OR.
Re leaving heat on all the time vs intermittent heating:
You say If you’re home is very well insulated, you are better off leaving the heating on at a set temperature, where the thermostat will work with the boiler to maintain the temperature relatively easily, since there is little heat loss occurring.
Do you mean to say that in this example, there is no energy saving when the house is only heated when needed?
As I understand my Physics, this argument doesn’t stand up. A house that’s only heated 50% of the time would consume less energy than if it were heated 100% of the time, surely?
Please explain
Thanks
Keith
I moved into a new 1 bedroom flat on 7th September just over 2 months ago and have had a really high gas bill of £375 and considering I only have the boiler on and have only started to have the heating on the last week i wonder where they get these figures figures from? I have given them meter readings but they are now doing a ‘Change Of Supply Dispute’ does that mean that the last tennant owes money and that’s why my bills are high?
Not sure how old these comments are, but has anyone ever considered this from the perspective of weather compensating modulating gas boilers (or outdoor reset, as it’s called in the US)?
WC constantly adjusts the boiler flow temperature to the outdoor temperature and, if set correctly, can exactly match the heat loss of the building in all temperatures. This enables the boiler to run at the lowest possible temperature and therefore maximise its efficiencies (in excess of 90% for mod-cons). However, it doesn’t work with setback, because it has no catch-up capability. Catch-up requires a boiler to exceed the building heat loss. Therefore, you can either (a) run WC; or (b) run set-back. You can’t do both. Therefore, with WC, you have to heat the building 24/7, but in fact, the boiler will run at the lowest possible flow temperature to maintain the set indoor temperature, and at times, the boiler will stop firing because the flow temperature is adequate to heat the building (at flow temperatures even lower than 30C). Plus, as the temperature is constant, most people are able to set it around 1C lower than intermittent heating, as the fabric of the building and furniture are also already warm.
Is intermittent heating more efficient than continuous when running WC? My guess would be intermittent is more efficient if the building is regularly unoccupied for relatively long periods (in which case, you’d have to run the boiler hotter to catch-up from set-back), but if the building is occupied most of the time, WC is probably the winner. It’s also considerably more comfortable, with no temperature swings as the room stat switches on and off around the set point (as it does for intermittent).
Sorry this artical is wrong. It is always more energy efficient to use the heating when it is required. So time clock with a room thermostate is best in every case. I can show the maths! I have also see the test data. To run a system all the tume will be more efficent on the system but will still cost you more!
Sorry this artical is wrong. It is always more energy efficient to use the heating when it is required. So time clock with a room thermostate is best in every case. I can show the maths! I have also see the test data. To run a system all the time will be more efficent on the system but will still cost you more! Unless maybe its only off for an hour a day. Insulation is key though so a lot of this artical is good. Check out bri website for accurate info
Is it worth using reflecting panels behind radiators on Party walll and external?
Hi Rinky,
Definitely worth it on external walls as they tend to leech heat, but also generally a good idea for party walls too! They easily pay for themselves over their lifetime.
Thanks,
TGA
We have a constant boiler and at this present time the boiler needs firing up manually at least twice a day if the boiler is turned off .(it will not come on automatically ) which is ok as its warm enough but we still need hot water. Will it be ok if we turn the radiators off and thermostat down and still enable the boiler to come on in order that we have hot water. Will this still waste money ?
I wanted to find out about heating my water. Should I have it on all day or only heat it in the morning & evening? This article only talks about central heating.
Nice blog. Thanks for sharing this with us.
I think that since the rate of cooling of a house is greater when hot more heat is lost if the heating remains on rather than turning it off.
I have a 3bedroom end terrace house, it’s very open plan,and I only have 4 radiators that work, will it cost a lot to keep them on all the time in the winter months.
thank you
We have a elm LeBlanc gas boiler that
Heats radiators and water. The boiler is 17 years old and is no problem. Will it need to be replaced for safety.
I had an old Leblanc boiler in a lettings house many moons ago and it was replaced with a Potterton Profile and more recently with a condensing boiler (which they all are now) and can recommend the Baxi Potterton which has a long guarantee and easy to fit and service etc
Plumbers also recommend Ideal Vogue ( I enjoy one in my home) and rather dearer the Worcester Bosch Greenstar and Vaillant Ecotech or Viessman boilers
Your page said if you don’t have a thermostat, you will likely be overheating your home when the programmer kicks in…. One will have to set the thermostat to high the max they want the room heated to. Set too low and the house feels cold, Thermostat could be a life saver if the house is too hot like the bedroom. My house has no thermostat inside and one morning woke up with my tongue sticking to the roof of my mouth, it all do the radiator was on full black during the summer, my bedroom door was closed, I live alone. Think I am lucky I lived !!!! You could cover this on your page too feel free to share my story.
still dont know what the amperage is for a vaillant ecotec pro
It will be more cost-effective to heat the home as and when you need it, as any heat you generate will be lost fairly quickly through the walls, so if you try and maintain that warmer temperature all the time, your boiler is going to have worked incredibly hard.
Interesting approach but you are not taking into account the moisture content of air in the property. Warm air holds a lot of moisture, and when the heating goes off, it condenses. In an old solid walled property, it is ESSENTIAL that the fabric temperature does not drop below dew point or you will experience damp problemsx – interstitial condensation in walls for eg, and mould. You NEED to keep walls above dew point – which for an average home in winter is going to be 10 degrees or more. This in turn means you need to keep the place heated to at least 15 deg C all the time – cyclical heating allows walls to cool down, and damp problems start. You can also look to control moisture by installing humidity controlled extraction in bathrooms and kitchens for eg., which drops moisture content of air, and lowers dew point.
Leaving it on is best & yes cheaper. Set thermostat at either 19-20-21 degrees.. My highest bill was £78 for the coldest month that was for my “gas & electric” & being in house 24/7 with C19. I leave living room/dining on 3 radiator temperature valve, sometimes I knock living room to 4. Main bedroom 3 sometimes 2
Bathroom 2,other bedrooms 2. House stays warm and bills work out a lot cheaper than turning on- off!! I have never used my fire since doing this either so saving big time.
agreed.
It is ALWAYS cheapest to not heat your home when you are not in it. Poorly insulated homes will save most.
Incorrect.
I have the Hive heating system installed and can see how many hours/minutes the boiler is on and when.
I’d always used the timer on in the mornings and evenings where the boiler would be on 3 to 4 hours a day due to the temperature dropping so much during the day and overnight.
i trialled having it on at a constant temperature of 19 degrees and the boiler now is only on for maximum 2 hours!
right now its 5C outsie and the heating came on automaticaly for 20 minutes at 6am (now 08:40). The room I’m in is at 18C and 49% relative humidity. So, I’m wearing a jumper.
Keeping humidity down by closing kitchen, utility and bathroonm doors and using extractor fans reduces both the amount of energy needed to heat the air but also reduced condensation on walls and windows. Especially in an older property, dampness on walls increases their thermal conductivity thus losing more heat. Humidity is a double whammy!
It is simply incorrect to say a well insulated home will use less fuel if the heating is left on. This is wrong. Whatever the level of insulation the amount of heat lost is proportional to the temperature difference between inside and outside. this is minimised if the heating goes off when not required.
O will be away for 5 weeks from late Feb until late March. What is the most economical way of leaving some heating on to prevent freezing?
Actually completely wrong!!! Do not follow this advice!!! Heat loss is greater the higher the temperature difference between inside and outside. Having insulation does not change this. Having insulation means that the temperature drop will be less when the heating is off and the fuel cost will be less to maintain a given temperature but there will never be a scenario where a higher average temperature through the day may be achieved at a lower cost. Certain power stations are different simply due to the cost of turning on and off ;e.g. nuclear). Very little or no extra energy required to start a house boiler. All goes into heat.
My home is very well insulated, I now just heat it 3 times a day for 1 hour period. It just retains the heat for hours once the house is warmed, so why have the boiler away all the time?
This 24/7 v on/off periods is one that has exercised my old mind for a while. At present I maintain an 18c temp 24/7 in a 23year old brick built house; it has excellent insulation and my bills are the envy of other people whenever the subject gets an airing – usually at this time of the year! I spend the vast majority of my time at home and 18c is usually among the lesser figures quoted so direct comparisons are inappropriate, but whatever the ‘correct’ answer is for me and my abode, no one mentions the comfort of a modest temperature (18c) constant v high temperature (>20c) on/off, health advantages of opposing methods, ages of occupants etc. Physics may answer the question of energy usage/costs given similar properties and equipment, but Physics alone will not provide the true costs/advantages of opposing methods. One cannot over value the pleasure, psychological and physical, I felt when I walked into my local the other day and saw a solid fuel burner, flames and all, and felt the blasts of heat from it – I could have stayed there all day! 🙂
Im in a 500year old solid stone wall concrete floors.
From off ( freezing!) up to 19 and resting at 18°c for about 7 hours and then turned down to 16°c is much cheaper. When the heating is off this house is freezing. In our last hot summer you needed a jersey to come indoors.
This house doesnt appreciate damp clothes so i use a tumble dryer which is cheaper than ironing ( compulsory for indoor dried clothes)
z
Really interesting to read the various peoples experiences, but it is, of course, comparing like apples and pairs as housing varies so much. I’m not going to tell you that what I do is best or cheapest BUT I am going to tell you what I’m doing this winter. Today is 1st December 2022, and this year I’m experimenting with the heating. In June in the UK, new regulations say that new boilers should be set to run at a maximum 55c. Well I’ve got a very old, non-condensing boiler and I wanted to see how well 55c would work. The house is 20 years old and pretty well insulated.
For 20 years, in the winter the boiler has been heating to 82c and programmed to run 9 hours per day (2 in the morning: 7 in the evening).
This year, (winter 2022) it is set to 55c and runs for 18 hours per day (roomstat & TRVs permitting).
The first “cold” month (November 2022) has just finished and the gas consumption in KWh is slightly less than my 5 year average for November.
Even if the gas consumption was slightly more, it’s so much more comfortable throughout the day that I would not go back to the earlier regime.
A modern boiler would be able to modulate down to a very low gas consumption and when a weather compensation sensor is added to minimise the gas burnt and controls to make the best use of the ability to modulate AND the condensing benefit that comes with the lower boiler temperature, it should be cheaper to run.
Don’t get carried away though. If your boiler works fine then keep it … unless you happen to have the most inefficient boiler on the planet. The savings from a more efficient boiler might take 40 years to pay for the boiler replacement, so not what I would call an “investment”.
PS – I do not believe all that man-made global warming stuff and zero carbon nonsense … it’s clearly a scam !
Can one permanently set a wall thermostat with a maximum limit e.g. 22 degrees, that cannot be increased.to a higher temperature via the wall thermostat?