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

richardc1983

I've done this years ago and for me in my home it was slightly cheaper to run constant at at a low temp. Even if we go away for the weekend pre covid rather than turning off to say frost we leave it set in low as it could be several days of the boiler running full tilt to bring the building envelope back up to temp. A lot of gas wasted. There is however a balance between what temp is right and how low you can tolerate. 
If we were to keep at 22c 24/7 then this would start to cost more than rinning constant at 19c etc. Everyone has to weigh up for themselves as no 2 houses are the same. 

2010

matelodave said:

2010 said:

Obvious thing to do is take a meter reading, set the thermometer to required temp and run it non stop for 28 days, then take a reading.
The following 28 days switch it on and off as needed and take another reading, then compare the two.

you also need to take lots of daytime and nighttime temperature readings to correlate consumption with temperatures

Don`t think so. 28 days in Jan/Feb would be near enough to give you a good idea what`s the best to do.
I doubt the consumption would be that close but enough to see which way is the cheapest.
Personally I switch it on and off as needed.
If it aint on it aint using.

Marvel1

On for 2 hours each morning and that's it, evening just wrap up with a hoodie.

orrery

coffeehound said:

Genuine question: ....Continuously running at a relatively low temperature with the boiler relighting infrequently to top up the water circuit temperature 'feels like' it should be more efficient ...

The proportional cycles tend to be over many 10s of minutes (mine tends towards an hour), so fairly infrequent. "Continuous running" may not be that continuous: the boiler is likely to heat at full power until it gets to its set temperature - what it does then depends on the boiler. Mine modulates back until it reaches its minimum power, then starts to go over-temperature until it shuts down - much of this will result in the return temperature being over that recomended for efficient condensing mode. The boiler restart sequence might then result in several restarts, as the return temperature will still be high and will likely throw it over-temperature again, before it restarts and will quickly go over the top again. Proportional control is intended to get over that.

Eco_Miser

roddydogs said:

Please stop resurrecting this hoary old thread.

You need to direct that to the MSE staff who put it in the latest newsletter.

Personally, I have the heating set to come on when the temperature is below 14c, which it's being doing this last week or so, and I switch to the 'daytime' setting only when I'm feeling cold.

coffeehound

Just to throw in another tidbit from Viessmann which supports the idea that switching the boiler on and off wastes some energy

These issues could make the thermostat take a false reading for the actual room temperature and it will force the boiler to shut down. Then, when the temperature drops again, it will start the boiler up. This constant on and off motion will waste energy as your boiler is always having to restart.

orrery

coffeehound said:

Just to throw in another tidbit from Viessmann which supports the idea that switching the boiler on and off wastes some energy

These issues could make the thermostat take a false reading for the actual room temperature and it will force the boiler to shut down. Then, when the temperature drops again, it will start the boiler up. This constant on and off motion will waste energy as your boiler is always having to restart.

The restart is such a short sequence it is difficult to see that it could waste so much energy as to be significant. I also don't see where such 'wasted' energy is going. It can't compare with the wasted energy of running a boiler when it isn't needed by not having it controlled by a central room-stat.

I remember being told as a teenager that fluorescent tubes were uneconomical because the turn on took a massive surge of energy. I doesn't take more than a few minutes will a calculator to work out that it simply can't be true, as the size of such a surge would blow the fuse in the time it took to start.

[Deleted User]

It’s a shame Mythbusters isn’t still going as the whole “Is it cheaper to leave your central heating on” debate would have been a good one for Adam and Jamie to put to the test. 

I actually really do miss that show 😔

super_skier

If you have a modern thermostat where you set the temperature you require rather than just timed on/off then your heating is technically always on. If you don't have one of these thermostats then you should as they save a lot of money with a modern modulating boiler.Our old house was a 1920s large semi with a new boiler eventually. We insulated everything including under the floor and sealed up all the gaps we could, halving our heating bills Setting temperature so that it came on low during the day cost around £8 per month more, definitely worth it for comfort. Our new house - near Passive House self build, has underfloor heating downstairs only, thermostat set to keep it at 21 degrees and only comes on around every other morning as it has dropped down to 20 degrees by then. Annual heating bill around £100, this is the way to go.

coffeehound

orrery said:
The restart is such a short sequence it is difficult to see that it could waste so much energy as to be significant. I also don't see where such 'wasted' energy is going. It can't compare with the wasted energy of running a boiler when it isn't needed by not having it controlled by a central room-stat.

I suppose there's the pump having to restart the water circuit flow from static, fan starting, ignition unit, maybe some unburnt gas.  As you suggest I don't suppose it's a big deal but having the whole system ticking along at lower temperature sounds preferable to having it chop on and off.  Almost certainly more wear and tear with that regime too.