Energy myth-busting: Is it cheaper to have heating on all day?

JohnSwift10

Astria said:

C_Mababejive said:

Its really simple and my best advice to everyone is that where possible, switch your heating OFF and with electricity, reduce your consumption. If you see it turned on and it isnt needed, switch it off.

The best way to save energy and money is to stop those meters turning.

Whilst that's true for electric, for heating it will always be "it depends".

I monitor how often and for how long my gas boiler runs for and how much gas I use, and turning it off makes next to no difference to leaving it on. It's more comfortable and convenient to leave it on so that's what I do.

What I've found is that (in my particular case) leaving the heating on causes the boiler to fire about once per hour, for about 10 minutes at a time. This seems wasteful as I'm typically out or in the office at work, but if I turn it off when I leave then it can take upto 2 hours to get the house back upto temperature, and the end result is that it's on for the same amount of time anyway.

The thermostat is set at 00:00 to 18:00 is 15c, and 18:00 - 23:59 at 18c, so still in the t-shirt and shorts range.

My wife and I are both in our 70's and normally in all day.

My heating is set to 21 deg C from 07:45 to 23:30 and 15 deg C the rest of the time.

I have found that myself about my gas boiler 10 minutes every hour or so.

I used to switch the heating off when I went out for an hour or 2  but discovered, like you, that the time to heat up the house took the same amount of gas as if the heating was never switched off i.e. if the heating was off for 2 hours it took 20 minutes to get it back to temperature compared to 2 10 minutes of heating.

Another thing about my heating is when the thermostat calls for heat during the day the water in the radiators isn't as hot as when it first switches on in the morning to raise the temperature from 15 deg C. if it even drops that low, compared to raising the temperature from 20 deg C to 21 deg C.

Now the only time I turn it off is if I am going to be out all day.

Petriix

Smart thermostats typically run the boiler in advance so as to achieve the desired temperature at the time you set. If I go out then I just tell it when I'll be back and it ensures the temperature is right for that time.

Obviously the lower the temperature differential between the house and the outside air, the less energy that is lost. So the longer the heating is off for, the greater the savings will be.

Cardew

Petriix said:

Obviously the lower the temperature differential between the house and the outside air, the less energy that is lost. So the longer the heating is off for, the greater the savings will be.

Absolutely correct.

As said many times in the frequent threads on this subject, you will use less energy if you switch off your heat source if you are leaving the property for 10 years, 10 months, 10 weeks, 10 days, 10 hours or 10 minutes - the laws of physics apply all the time.

That statement is normally a cue to those who have an extensive understanding of the charachteristics of their gas boiler and property under all external and internal conditions and know to the nearest minute if the condensing/lack of condensing performance of their particular boiler negates the above statement.

What is more they have proved their point by trials under carefully controlled conditions; peer reviewed by the wife

 

Astria

Petriix said:

Smart thermostats typically run the boiler in advance so as to achieve the desired temperature at the time you set. If I go out then I just tell it when I'll be back and it ensures the temperature is right for that time.

Yes, I turned that off on my hive system as it was very annoying - it switches the boiler off before it hits the desired temperature then decides that the residual heat didn't quite get it to the desired temperature 10 minutes or so later so switches it on again for a short term (which can be a few minutes), then because the residual heat is pretty much gone by that point it's already dropping and it comes on again 15 minutes later. Disabled that logic and now it just stays on until it hits the set temperature then goes off, coming on again when it drops below the set temperature. Much easier, much simpler, and the boiler only has to switch on once per hour. Only disadvantage is that the eventual temperature can be 0.7c hotter than requested for a small amount of time.

Heinzbean

Its all Maffs.

i am experimenting at the moment last year i used the central heating as it was designed to be used.Set the stat to 18". and let it do its stuff. old mechanical stat in the hall.......house is warm at this 18". setting.house double glazed and well insulated.Also in 20-minutes the rads are barely touchable.

 So if my boiler costs 24Kw x 21.37p = costs £0.96 per hour to run.
 8-00clock  could take 30 minutes to 50 minutes to get to 18" depending on temperature outside.
 lets say 50 minutes to get house up to 18"
 8.00 -8.50 = £0.80p
 10.50-11.10= £0.32p
 13.10-13.30= £0.32p
 15.30-15.50= £0.32p
 17.50-18.10= £0.32p
 20.10-20.30 =£0.32p
 This would cost = £2.40 + 26p daily rental =£2.66 per day x31 days = £82.46 per month..

20 minute blasts when needed. Lets say 5 x 20 minute blasts.  0.96/3 =£0.32p X5 =£1.60

 This would cost =£1.60 +26p daily rental= £1.86 per day x31days=   £57.66.

Will i be colder i doubt it but what is definite it will be cheaper.

Well this is a money saving site.

orrery

Heinzbean said:

i am experimenting at the moment last year i used the central heating as it was designed to be used.Set the stat to 18". and let it do its stuff. old mechanical stat in the hall...

Interesting. If your boiler is 'condensing' then you may wish to break up the boiler runs to ensure that it stays in condensing mode, i.e. that the return temperature stays low. I'm not sure what sort of boiler it is - I can't fathom the "24kW x 21.37p = £0.96 per hour".

The statement that the radiator are barely touchable might indicate that it isn't in condensing mode, and therefore costing you more to run than it should.

I break up every hour so that it runs for 40 minutes and is off for 20 minutes, which keeps it in condensing mode, but this requires an intelligent controller. The controller also tries to proportionally control the boiler, so will wait a certain delay after starting an 'on' period before it kicks in, depending on roomstat measurement. The result is that the boiler can only run for 40 minutes, and it will only try to do that when the system is cold, and when maintaining the temperature it will run for about 5 to 20 minutes in any one hour.

Cardew

Heinzbean said:

Its all Maffs.

i am experimenting at the moment last year i used the central heating as it was designed to be used.Set the stat to 18". and let it do its stuff. old mechanical stat in the hall.......house is warm at this 18". setting.house double glazed and well insulated.Also in 20-minutes the rads are barely touchable.

 So if my boiler costs 24Kw x 21.37p = costs £0.96 per hour to run.
 8-00clock  could take 30 minutes to 50 minutes to get to 18" depending on temperature outside.
 lets say 50 minutes to get house up to 18"
 8.00 -8.50 = £0.80p
 10.50-11.10= £0.32p
 13.10-13.30= £0.32p
 15.30-15.50= £0.32p
 17.50-18.10= £0.32p
 20.10-20.30 =£0.32p
 This would cost = £2.40 + 26p daily rental =£2.66 per day x31 days = £82.46 per month..

20 minute blasts when needed. Lets say 5 x 20 minute blasts.  0.96/3 =£0.32p X5 =£1.60

 This would cost =£1.60 +26p daily rental= £1.86 per day x31days=   £57.66.

Will i be colder i doubt it but what is definite it will be cheaper.

Well this is a money saving site.

You are incorrectly making the assumption that your boiler oputputs 24 Kw to radiators when it is firing.

QrizB

Cardew said:

You are incorrectly making the assumption that your boiler oputputs 24 Kw to radiators when it is firing.

They made the same incorrect assumption in another thread too.

It would also be interesting to know if Heinzbean's gas bill for the month is anywhere near £82 pm.

Heinzbean

whoops put electric kwh rating should have been 0.0401 per kwh

Heinzbean

Its all Maffs.Shame im no good at maths. i have put the proper kwh figure in.

i am experimenting at the moment last year i used the central heating as it was designed to be used.Set the stat to 18". and let it do its stuff. old mechanical stat in the hall.......house is warm at this 18". setting.house double glazed and well insulated.Also in 20-minutes the rads are barely touchable.

 So if my boiler costs 24Kw x 0.0410 = costs £0.96 per hour to run.
 8-00clock  could take 30 minutes to 50 minutes to get to 18" depending on temperature outside.
 lets say 50 minutes to get house up to 18"
 8.00 -8.50 = £0.80p
 10.50-11.10= £0.32p
 13.10-13.30= £0.32p
 15.30-15.50= £0.32p
 17.50-18.10= £0.32p
 20.10-20.30 =£0.32p
 This would cost = £2.40 + 26p daily rental =£2.66 per day x31 days = £82.46 per month..

20 minute blasts when needed. Lets say 5 x 20 minute blasts.  0.96/3 =£0.32p X5 =£1.60

 This would cost =£1.60 +26p daily rental= £1.86 per day x31days=   £57.66.

Will i be colder i doubt it but what is definite it will be cheaper.

Well this is a money saving site.