Gas central heating - Cheaper to leave on constant or switch off when not using it?

Veni Vidi Vici

Well-known Member
Hi all

Is it cheaper to leave your gas central heating on all the time (on a low temperature) or switch it off and turn it back on when you need it?
 

deckingman

Well-known Member
Hi all

Is it cheaper to leave your gas central heating on all the time (on a low temperature) or switch it off and turn it back on when you need it?

Not an easy question to answer. In theory, you'd think only switch it on when you need it. However, from experience, before we had kids, we were both out at work all day, so had the heating set to go off and come back on just before we got home. Then, when the first sprog came along, we had to have the heating all the time as my wife was at home and remained so until the sprog started school. I thought that it was going to cost a bomb, but in fact we saw no difference in the heating bills at all.
 

mda1974

Active Member
I asked this question to a British Gas engineer who came to service our boiler just after we moved into our house.

He said it was better to leave the heating on all the time and control it by the thermostat and the thermostats on the individual radiators.

I don't know if this is the same for all boilers but I guess it would not necessarily be the case if you do not have thermostats in each room
 

Veni Vidi Vici

Well-known Member
Thanks. I guess if you switch it off and let the house get cold then it will take longer to heat it up again. I've had mine on pretty much all the time in the last 3 months, think I'll just turn it right down when it gets too warm instead of turning it off and see what happens when I get the bill in.
 
D

Deleted member 293381

Guest
The big factor is - how well the house is insulated. If it's well insulated the temperature drop is less when the CH is turned down at night.

For example, we have our CH at about 20 deg C during the day and 16 deg C at night. When there is frost outside the CH doesn’t switch on at night, only when the outside temp at night reaches about -5 deg C does the CH come on.

The other factor is not to have a steep temperature gradient between rooms in a house. In other words, all rooms about the same temperature. The upstairs can be a lower temperature than downstairs because heat rises up the stairwell.

It's a well insulated house that saves money in heating costs and the residual heat from the day keeps the house cosy at night.

So, to answer the question, leave it on!
 

deckingman

Well-known Member
Thanks. I guess if you switch it off and let the house get cold then it will take longer to heat it up again. I've had mine on pretty much all the time in the last 3 months, think I'll just turn it right down when it gets too warm instead of turning it off and see what happens when I get the bill in.

Those are my thoughts. It takes a certain amount of energy to raise the temperautre of an object. So if you want to raise it say 1 degree every hour, it'll use the same energy as raising 5 degrees after 5 hours. Maybe a bit simplistic but it explains what actually happened in our situation.

Nowadays I have a programmable 'stat which gives me 4 different temperatures a different times of the day, so effectively it's "on" 24/7 all year. e.g. If there is a cold morning in June it'll come on but conversely, if there's a warm afternoon in December, it won't.
 

DPinBucks

Distinguished Member
It's simple physics (oh Gawd, not again, I hear you cry!)

If you don’t need the heat, turn it off. A warm house loses more heat than a cold one. If you turn your heating off overnight, and it’s cold in the morning, then obviously if you’d left the heating on then you’d have been paying to waste heat.

Experiment. How long does it take to heat the house from cold to an acceptable temperature? If that is shorter than your average sleep time, then set your timer to go off about 30-60 minutes before you go to bed, and the appropriate time before you get up. Anything else is simple waste.

On the other hand if your house doesn’t cool off significantly overnight, then you have very good insulation, and it won’t make a lot of difference what you do. Conversely, if it takes ages to heat up then your house is insufficiently insulated; so fix that as a matter of priority.
 

Bill Hicks

Banned
Not sure bout your heating but I was told by a council engineer that it's better to leave your water boiler on constant as the amount of Gas needed to heat it up from hours earlier is more than it is to leave it ticking over on constant.

Prob works on the same principle with heating the house.
 

neilneil

Active Member
Not sure bout your heating but I was told by a council engineer that it's better to leave your water boiler on constant as the amount of Gas needed to heat it up from hours earlier is more than it is to leave it ticking over on constant.

Prob works on the same principle with heating the house.

That Council 'engineer' was talking rubbish.
DPinBucks has the right answer. The physics behind it is actually pretty obvious.
The first law of thermodynamics says that the exchange of heat between to bodies is proportional to the temperature difference between them.
i.e. place a really hot rock in a cold cup of water then there is a rapid exchange of heat. But, place a warm rock in a warm cup of water then the heat exchange between them is pretty low.

So, if it's 20 degrees inside your house and it's -5 outside then the heat loss is going to be greater than than if it's 10 degrees inside and -5 outside. All other things being equal. Of course the rate at which each house looses heat is dependant on how well insulated it is.

-Neil
 

Veni Vidi Vici

Well-known Member
That Council 'engineer' was talking rubbish.
DPinBucks has the right answer. The physics behind it is actually pretty obvious.
The first law of thermodynamics says that the exchange of heat between to bodies is proportional to the temperature difference between them.
i.e. place a really hot rock in a cold cup of water then there is a rapid exchange of heat. But, place a warm rock in a warm cup of water then the heat exchange between them is pretty low.

So, if it's 20 degrees inside your house and it's -5 outside then the heat loss is going to be greater than than if it's 10 degrees inside and -5 outside. All other things being equal. Of course the rate at which each house looses heat is dependant on how well insulated it is.

-Neil

So leave it on or switch it off?
 

DPinBucks

Distinguished Member
So leave it on or switch it off?
Sorry, I thought Neil & I had made that clear.

Switch it off.

Let's say it takes half an hour to warm your house from cold, and you normally get up at 07:30. Then set it to come on at 07:00. If you go to bed at 22:30, then set it to go off at 22:00. Adjust the times with experience. If necessary, get a timer which allows you to make different settings for weekends, when you might get up and go to bed later. Also, if the house is empty during the working day, get a two-level timer and treat the empty period the same as overnight. Generally in my experience, hot water timing need be the same as heating, but that's a matter of personal requirements.

Anything else is waste.
 

TylerDurden

Well-known Member
Why not just try it over a couple of weeks, one week on 24 hrs, the other week on timer, check your meter readings before and after. I did that during the recent cold period and my useage rose a lot over the week I had the heating on 24 hrs
 

Coffin

Distinguished Member
Switch it off.

Let's say it takes half an hour to...
This is pretty much what I do although live alone in a modest 3 bed semi so only have to accomodate myself.

I wake up at 7.15am, so the radiators come on at 6.30. I get home from work at 6.30pm so they come on at 5.30. Go to bed around 11.30pm most nights so they go off at 10. If the weather gets extreme (as it was a couple of weeks ago) I'd adjust accordingly.

My parents whilst home in the day leave theres on 24/7 and the bills are horrendous!
 

deckingman

Well-known Member
Sorry, I thought Neil & I had made that clear.

Switch it off.

Let's say it takes half an hour to warm your house from cold, and you normally get up at 07:30. Then set it to come on at 07:00. If you go to bed at 22:30, then set it to go off at 22:00. Adjust the times with experience. If necessary, get a timer which allows you to make different settings for weekends, when you might get up and go to bed later. Also, if the house is empty during the working day, get a two-level timer and treat the empty period the same as overnight. Generally in my experience, hot water timing need be the same as heating, but that's a matter of personal requirements.

Anything else is waste.

That's the theory. In practice, as I stated earlier, we found no difference between having the heating on "timed" for morning and evening, and having it on all day. That was comparing gas useage over a 3 year period prior to the change in timer setting and a further 2 year period after.

Clearly, there are other factors to take into account such as boiler (and radiator) efficiencies at different tempertures. You can also get temperature over swings caused by the radiators being very hot, the thermostat going off, but the latent heat continuing to heat the room beyond the set temperature.

I'm not sure of the exact mechanisms involved, but it's not quite so simple as the "basic physics".
 

JudeXbox

Standard Member
If in a wet system the tempreture has to be raised from a low tempreture to the desired
Tempreture the energy required to do so will be proportional to the rate of at which water resists tempreture increase. Water naturally resists tempreture rises with larger capacity . It also takes more energy to increase tempreture the higher the inintial tempreture. It also cools down quicker the hotter it is. Therefore it could be rationaled to reduce the energy expenditure reduce the disired tempreture and reduce the capacity. A stable constant temperature could therefore be maintained constantly at lower cost provided the heat lost from the system was negligible.
If you loose 20% of the heat from the system it takes 20% of the energy to maintain the temperature. If you loose 100% it takes 100%. The rate of heat loss has to be so low so as to require lower expenditure of energy than switching off then reheating. If the rate of heat loss is too high it would be cheaper to switch off then reheat.
 
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lurcher

Well-known Member
Just done a trial for 3 weeks with the heating on all the time temperatures controlled on the radiators , meter readings have gone up considerably.
Reverting to off with programme on at 0630/8.00am daily
 

KhalJimbo

Distinguished Member
I did this last winter as a test and thought I'd turn my boiler on, leave my thermostat to 18c and see how it goes.

My winter gas bill was £450 for single person in a 2 bedroom flat!! I pay quarterly and its never above £200 even in winter with my usual program which is on at 17:00 to 22:30 - then from 04:30 - 07:30.

I'm reverting back to my normal heating routine and I'm gonna be tighter than a ducks ass this year with my gas I can tell you that!
 

lurcher

Well-known Member
I am retired so in most of the day , heating came on at 6.30am and off at 8am , its 16c at the moment in living room which I am comfortable with .
Firing up the log burner mid aft so its warm when the workers come home at 4pm , going to see how that works cost wise.

Julian
 

Berties

Banned
yeah if I were to set it to 18 degrees it'll come on even though it feels warm enough. Feel fine at 16, when it's 11-14 that's when it comes on raise it back to 16.
 

baldrick

Well-known Member
Our thermostats have 4 settings:

Wake
Away
Home
Sleep

They came pre-programmed with the optimal Energy Star settings which I'm assuming are calculated for a house that meets Energy Star standards (ours does).

Net result is that 'Wake'/'Home' are your active heating/cooling (we have air conditioning of the summer) periods and 'Away'/'Sleep' have 'set back' temperatures to ensure the house doesn't get too hot or cold.

Right now we're all out of the house so the systems are effectively off unless the temp drops too low and they will kick in to get the house ready for when we get home.

They also aim to have the house at the desired temp at the time you set, so if you say 70F at 5pm it will learn how long it needs get from current temp to desired and kick into life at 4.40pm...
 

njdbaxter

Well-known Member
This is pretty much what I do although live alone in a modest 3 bed semi so only have to accomodate myself.

I wake up at 7.15am, so the radiators come on at 6.30. I get home from work at 6.30pm so they come on at 5.30. Go to bed around 11.30pm most nights so they go off at 10. If the weather gets extreme (as it was a couple of weeks ago) I'd adjust accordingly.

My parents whilst home in the day leave theres on 24/7 and the bills are horrendous!

coffin has the right idea

i set mine to auto, at 5:30am its set to increase to 20 for a hour, then at 10:00pm for 1.5 hours

between 6:30am and 10pm its set at 12 degrees so heat will turn on if it goes below 12, it never has
 

Noggin1980

Distinguished Member
+1. :rotfl:

Though I'm probably biased as I've just notched up a gas bill of £177 for 1 month's use. :(

My winter gas bill was £450 for single person in a 2 bedroom flat!! I pay quarterly and its never above £200 even in winter with my usual program which is on at 17:00 to 22:30 - then from 04:30 - 07:30.

That's mad, are you sure it's not a load of estimated readings followed by an actual? or maybe you've never switched tariff and are on a really expensive one.

We have a 3 bedroom house (4 if you include the extension) which isn't greatly insulted especially as the garage is now the kitchen, we have the heating on all day on about 25 degrees (I'm disabled and feel the cold alot) from 5am-10pm and our yearly gas bill is about £600. I can't believe there is many people who use more heating than us without having a massive house.
 

SBT

Banned
Ours only has two settings ON FULL BLAST when the wife is in.OFF when she's out :laugh:

I really don't know how women can feel that cold all the time :confused:
 

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