Heating on during the night does not use any more gas.

Posts: 259
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The past week the outside temperature where I live has never been above 0 deg C during the night and as a result when my heating "goes off" (the thermostat is set at 12 deg C from 23:30 to 07:45)  by 07:45 the downstairs temperature has dropped to 14 - 15 deg C .and when the heating comes on again at 07:45 it takes about an hour to an hour and a half to raise the temperature to 21 deg C before the boiler cuts off then cycles on and of for the rest of the day until 23:30.

So I have manually been setting the thermostat to 18 deg C from 23:30, every second night (I haven't figured out how to permanently change the temperature on the thermostat)

I have a thermometer sensor that records the temperature and time (Switchbot) and around 04:00 that is when the temperature sinks to 18 deg C and the heating comes on and maintains the temperature.

When 07:45 happens the thermostat switches to 21 deg C and it then only takes 30 - 45 minutes to raise the temperature to 21 deg C.

When I downloaded my gas usage from n3rgy.com and compared the gas usage between the days the heating was on at 18 deg C during the night and not there was no discernible difference in gas usage.

So when I figure out how to alter the thermostat I will have the night time temperature at 18 deg C.

My conclusion from my little experiment was that if you have your heating on all day for 15 3/4  hours switching it off during the night is not going to save if any much gas.

The same with switching it off for 3 hours when I go out on a Saturday night.

On the 3 days of figures shown the outside temperatures were below 0 deg C as each morning there was frost on car windscreens

02-Dec
00 0.042
01 0
02 0
03 0
04 0
05 0
06 0
07 0
08 0.875
09 0.725
10 1.394
11 0.616
12 0.282
13 0.35
14 0.361
15 0.332
16 0.317
17 0.31
18 0.07
19 0
20 0
21 0
22 0.71
23 0.533
02-Dec Total 6.917

03-Dec
00 0.038
01 0
02 0
03 0
04 0
05 0
06 0
07 0
08 0.883
09 0.605
10 0.827
11 0.712
12 0.494
13 0.283
14 0.239
15 0.327
16 0.36
17 0.333
18 0.334
19 0.251
20 0.25
21 0.326
22 0.29
23 0.061
03-Dec Total 6.613

04-Dec
00 0.051
01 0
02 0
03 0
04 0.191
05 0
06 0.192
07 0.1
08 0.752
09 0.678
10 1.099
11 0.354
12 0.204
13 0.302
14 0.354
15 0.322
16 0.208
17 0.33
18 0.302
19 0.077
20 0.209
21 0.233
22 0.22
23 0.187
04-Dec Total 6.365
«1

• Posts: 5,792
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According to doctors, falling asleep with the heating on can result in a restless night's sleep as our bodies can overheat much more quickly. As well as not being able to sleep soundly, it may also be causing our skin to appear dry, red and itchy the following morning.

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According to doctors, falling asleep with the heating on can result in a restless night's sleep as our bodies can overheat much more quickly. As well as not being able to sleep soundly, it may also be causing our skin to appear dry, red and itchy the following morning.

Unless i missed it they don't even say what temp is bad! Waking up at 13c is hardly healthy either!

I think 18.5c is a perfect temp for sleeping.

""We're only talking about a half to one degree [Celsius] (32.9°F-to-33.8°F) but that small temperature change can result in significant differences in arousal between insomniacs and people without sleeping problems.""
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edited 6 December 2023 at 6:37PM
markin said:
Unless i missed it they don't even say what temp is bad! Waking up at 13c is hardly healthy either!

I think 18.5c is a perfect temp for sleeping.

""We're only talking about a half to one degree [Celsius] (32.9°F-to-33.8°F) but that small temperature change can result in significant differences in arousal between insomniacs and people without sleeping problems.""

I am lucky if it reaches 18.5*c during the day, my reading is now showing 13.6*c, the heating has been on, for a few hours.
Perhaps it's the radiator/fires just being on that dries out the air. My central heating is set to 21*c during the day and off when I go to bed, but it rarely reaches 20*c. I work some hours during the day, so I doubt it would save me money to have the heating on 24/7, but it would help the house stay warmer.
But its better to be outdoors doing stuff, maybe when I am retired I will have the central heating on 24/7
• Posts: 2,071
Forumite

My conclusion from my little experiment was that if you have your heating on all day for 15 3/4  hours switching it off during the night is not going to save if any much gas.

That's an interesting set of real world data.  You could optimise it a bit more in your 18 Deg.C overnight scenario by setting the start time a bit later so it reaches the daytime 21.0 target at around the same time.

Interesting because the science is quite clear, heat loss due to conduction is proportional to the temperature difference.  So with outside air at 0C and inside at 18C it will be losing heat faster than with inside air at 14C.

So why doesn't your result reflect this?

One factor may be that the actual differences aren't that great. The temperatures are the same all day and overnight until 04:00 where one scenario brings the heating on to maintain 18C, the other lets it continue to cool reaching 14C at 07:45. A mean difference of around 2.0 degrees for 3.75 hours. Plus a small difference in the morning since the 18C scenario brings it up to 21C earlier.

So something must be offsetting those differences.  Could it be that the boiler runs more efficiently, more of the time in condensing mode?

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Very interesting!
My conclusion from my little experiment was that if you have your heating on all day for 15 3/4  hours switching it off during the night is not going to save if any much gas.
I'm not entirely sure you can draw this conclusion from the data you've shared.
Here are the temperature records from Southampton airport (relatively close to me):

December 2nd was much colder than the 3rd, which was a little colder than the 4th.
Is there an airport (or another reliable weather station) near you that can provide similar data for your loction?
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THis reminds me of the long long thread that ran for about 10 years:
People tended to be divided into two camps. The "it costs you money whenever your heating is on" or the "it saves you money keeping your house at a certain temperature".
Opinions have perhaps changed a bit now in that, as the OP has found, it does not cost you much extra at all to maintain a certain temperature overnight instead of having the heating off. Particularly with modern condensing boilers that operate more efficiently when maintaining a temperature as against working hard to raise the temperature.
Doing any analysis is hard because of other variables such as outside temperatures and weather in general. Individual experiments and analysis over lengthy periods of time can give people a feeling of what is best for them, but not so many people can do that.
That's just my opinion though!

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• Posts: 2,332
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victor2 said:
THis reminds me of the long long thread that ran for about 10 years:
People tended to be divided into two camps. The "it costs you money whenever your heating is on" or the "it saves you money keeping your house at a certain temperature".
Opinions have perhaps changed a bit now in that, as the OP has found, it does not cost you much extra at all to maintain a certain temperature overnight instead of having the heating off. Particularly with modern condensing boilers that operate more efficiently when maintaining a temperature as against working hard to raise the temperature.
Doing any analysis is hard because of other variables such as outside temperatures and weather in general. Individual experiments and analysis over lengthy periods of time can give people a feeling of what is best for them, but not so many people can do that.
That's just my opinion though!

I think everyone agrees that whenever the boiler is actively heating it costs you money - and no one is advocating having the heating 'always on' (aka the boiler constantly running) but there is a reasonable question if using a thermostat, a programmable thermostat, or manually turning the heating on/off saves money.

The answer to that HAS to depend on the desired temp (or temps for different times of day) vs the number of hours you want the property at that temp (how many hours a day is someone in the house) vs how quickly your house loses heat (which depends partly on ambient temp, and thermal mass of the property) vs how quickly your heating system can replace that heat and bring the property back to temp (which depends partly on rad size and flow temp, plus again thermal mass)...
I'm not an early bird or a night owl; I’m some form of permanently exhausted pigeon.
• Posts: 1,446
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My heating currently runs at 17c from whenever I wake up (normally between 8am and 10am) to whenever I go bed (which is typically 1-2am) and 15c whilst I'm in bed. According to HIVE, the heating is typically on for 10 - 11 hours per day at the moment during the cold temperatures, which uses up (according to my gas meter) 50 kWh/day, so about £3.25 per day, less than it would cost me to sit in a coffee shop.
I compared this to the days when I travelled to work, turning the heating off instead during the day. The cost per day did decrease, by about 15p/day, but I'm more than willing to pay that for convenience - when the house has dropped to 11 - 12c during the day it certainly takes a number of hours to bring the temperature back to comfortable, and then warm everything else back up again. For some strange reason I actually think the house also smells better when kept warmer too!

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I think a more meaningful analysis would look at the gas consumption from the time it went onto setback at 23:30 until the time it was stabilised at occupancy temperature next morning, say up to the 10:00 figure. Any differences in consumption outside those times will be unrelated to whether you set back to 12C or to 18C.

It's not clear from the post which day(s) were set to 12C and which to 18C. The first two days didn't fire until 08:00, either those were both 12C or the weather was such that the house didn't cool below 18C.
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JohnSwift10 said: So I have manually been setting the thermostat to 18 deg C from 23:30, every second night (I haven't figured out how to permanently change the temperature on the thermostat)

So when I figure out how to alter the thermostat I will have the night time temperature at 18 deg C.
You want to invest in a programmable thermostat - These allow you to set different temperatures throughout the day/week. Perhaps something like the Drayton Wiser.
I have a smart control system, and have it set for 17°C overnight, and then 19°C for most of the day. Weekends, it will go up to 19.5°C for a few hours in the evening.
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