Turning off heating for short periods is not worthwhile

WhoisDannie

I go out most mornings for an hour and started turning off my heating (radiators and combi boiler) and then on again when I returned and started to keep note of my gas usage and discovered that when I turned my heating on again the gas usage in the next hour was more than what was usually used in an hour when the heating was left on continuously.
.
So instead of using 2 kWh each hour for 3 hours, total 6 kWh, it used 2kWh then 0kWh then 4 kWh so still 6 kWh.

I also noticed the same when I went out in the evening for 2 hours, the usage in the hour or so when I turned the heating on again was about what was normally used for the previous 2 hours.

So how long does the heating need to be off to make it worthwhile?

Brie

When it was really cold I changed the heating to be on non stop instead of the previous being off from 10 pm to 6 am.  We also used to have the heating off during the day - when we both were out and only needed enough heat to keep the cats comfy.  

But this winter's cold meant we had the heat on all day even if we were out or away for a few days.  This was because it was impossible for our house to warm up sufficiently to be bearable.  By having it on 24/7 we could maintain a fairly steady 18c and could just add a small electric blower if we were sitting about and feeling the chill.  

No idea what the actual readings say about this as I have no way to check them easily.  

ariarnia

it really depends. if you have your boiler 'on' with a thermostat then it will come on and off anyway. depending on how your house is insulated then there might be an hour or 2 when its not actually 'on' just because the temp hasn't dropped enough. for that time theres no 'point' turning on and off because the boiler will run the same both ways.

so the point where you save MONEY is when the boiler is not burning for long enough that it uses less energy to get back to temp than to keep to temp and thats not something thats going to be the same between differnt houses/boilers. or even differnt days because the rate of loss is depending on the temp inside compared to the temp outside.

for me tho its about more than money. we run our heating on constantly on low (about 14/15 degrees) between november and feb (ish). thats because we could probably save a little money by turning it on and off or on a timer but then we have times when it gets uncomfortably cold while we wait for the house to heat back up. so we would rather save money by having a low background heat than cost money heating the house hotter because we 'feel' cold so wack up the thermostat to 22 for an hour or 2.

theres no real right or wrong or one size fits all   

km1500

I have a friend with a small house whose gas heating is on all day (7am to 8pm) and the IHD reads pretty much constantly £6 per day gas usage.

I tried turning it off at 10am when leaving the house and back on at 3pm when arrived home. The cost was £5.50 for that day.

FreeBear

ariarnia said: for me tho its about more than money. we run our heating on constantly on low (about 14/15 degrees) between november and feb (ish). thats because we could probably save a little money by turning it on and off or on a timer but then we have times when it gets uncomfortably cold while we wait for the house to heat back up. so we would rather save money by having a low background heat than cost money heating the house hotter because we 'feel' cold so wack up the thermostat to 22 for an hour or 2.

theres no real right or wrong or one size fits all   

I have a baseline temperature of 16-16.5°C and a slot programmed for an hour or so in morning & evening to boost it up to 18°C (thermostat is in the hallway). If the sun is shining, I can get it up to ~19°C in the lounge or light the fire for a bit of extra heat. Over the last month, the boiler has been firing up for around an hour in total each day - Had a few days when the boiler didn't even come on..

Not everyone can benefit from solar gain, so my heating schedule won't work for many. But it is still worth having a programmable thermostat so that you can set different temperatures depending on time of day - Research suggests that an average household could save 10-15%. Reality indicates a figure closer to 2-5%.

MikeJXE

I guess it depends on the property. 

I was in a 1st floor 2 bed flat EPC B was very careful not to use the gas, no cooking heating on only when I got cold, anything from an hour a day to 4 hours a day

I have moved to a ground floor 1 bed flat EPC B I'm experimenting 

I sleep on and off at all times, I normally go to bed about midnight and switch the thermostat to 10 degrees, when I get up which can be any times even 2 o'clock or 4 o'clock 6 o'clock I set the heating at 18/19 degrees and there it stays till I go to bed 

I keep accurate readings on a spreadsheet and over the last 3 weeks the consumption is  slightly less than my 2 bed but I am warmer all the time, for gas the readings for the last 3 weeks were 159 124 and 102kwh so I guess it's getting warmer as I have not changed my plan 

ariarnia

FreeBear said:

ariarnia said: for me tho its about more than money. we run our heating on constantly on low (about 14/15 degrees) between november and feb (ish). thats because we could probably save a little money by turning it on and off or on a timer but then we have times when it gets uncomfortably cold while we wait for the house to heat back up. so we would rather save money by having a low background heat than cost money heating the house hotter because we 'feel' cold so wack up the thermostat to 22 for an hour or 2.

theres no real right or wrong or one size fits all   

I have a baseline temperature of 16-16.5°C and a slot programmed for an hour or so in morning & evening to boost it up to 18°C (thermostat is in the hallway). 

i think we're probably very similar but for us its the stove in the lounge in the evening if needed which brings up the temp of the rest of the house. 

Mstty

Low and slow is best for people at home a lot. If you are out to work for long hours you can turn off and blast.

kipperman

If we are away from home for a week the nest thermostats revert to Eco mode and maintain 12 degrees. I'll switch back to home mode a day or so before our return - but the energy usage to get the house back to it's "usual" temperature is significant. I know the why's ( SHC of walls etc) but anecdotally at least I wonder if it's just worth leaving on the home setting - plus the fact that the house doesn't feel warm for at least a couple of days.

Max68

When it was really cold I did a mini experiment.  One morning my house was at 13c so in the morning (heating off) I put thermostat to 17 and it took around an hour and a half/two hours to get up to that.  The next night it was around 16c when I went to bed so I put thermostat at 14.5 all night.  Next day I had used far more gas leaving low overnight than I did blasting it for a couple of hours.  Was surprised to be honest as I assumed the harder the boiler worked the more you would use but not so for me anyway.  Not a one size fits all, suspect it depends on house, insulation, type of boiler etc.

ariarnia

Max68 said:

When it was really cold I did a mini experiment.  One morning my house was at 13c so in the morning (heating off) I put thermostat to 17 and it took around an hour and a half/two hours to get up to that.  The next night it was around 16c when I went to bed so I put thermostat at 14.5 all night.  Next day I had used far more gas leaving low overnight than I did blasting it for a couple of hours.  Was surprised to be honest as I assumed the harder the boiler worked the more you would use but not so for me anyway.  Not a one size fits all, suspect it depends on house, insulation, type of boiler etc.

not sure about your house but ours doesnt just 'drop' and stay low over night. just like in the day theres a natural curve to the temp. so it might be warm when we go to bed. then cool and get to cold at like 1am before warming back up a bit by morning. so your boiler might not of been maintaining just 1.5 degrees all night. its why even when our thermostat is 'off' its set to the frost free setting. a cold night in march could still get to minus temps outside for an hour or 2.