Constant heating at lower temp vs short bursts at higher temp

GlacialDrift

My flatmate and I are trying to work out the most cost-efficient method of heating our flat this winter. We have gas central heating. Two ideas we have are:

- Generally on all the time while someone is in the flat (evenings / weekends), say 18 to 21 degrees.

- Short bursts of 30 mins to an hour when needed at a higher temperature, say 24 to 28 degrees.

Any ideas which will be the more cost efficient, or any other suggestions?

Thanks in advance.

rogerblack

The setting of the thermostat makes no difference in most cases, if the boiler is on.
It's either under temperature, or on.
If it's on, it doesn't matter if you turn the thermostat way up - it uses the same amount of power.

Anyway - the total heat needed to heat the property at any moment is pretty much a constant number times the difference between the inside and outside temps.

This means that the total energy needed to heat the property over the day is proportional to the average difference in temp between inside and outside.

If you have it peaking at 28C difference, but the average is 18C, you will use about the same energy as if you simply set it to 18C, and leave it.

From a comfort POV - set it at 18C, and leave it.
Get used to that temperature, and wear a light jumper if you feel chilly.
Putting it up high for short periods will only make you feel cold when it turns off.

grahamc2003

Depending on your lifestyle, work times, location of thermostat, and countless other factors, you could start with a base situation, and make small modifications from there to suit you. A good start point in my view would be to set the temp to 18C from 05:00 to 08:00 and 16:00 to 22:00, and 5C from 08:00 16:00 and 22:00 to 05:00 (weekdays, but you get the idea). If it doesn't suit after trying for a few days, make small changes (i.e. half hour earlier or later, or one degree warmer or cooler) and try again for a few days.

Turning it to 28c for half an hour is pointless and will just supply 30 minutes of constant heating which you may not need at that time, so would cost you more.

Pincher

Efficiency
________

You want to recover waste heat through condensing mode to increase efficiency. This means steady state, low flame, low return flow temperature.

Let us assume 90% efficient when condensing, and 70% when not condensing.

Heat loss
________

The flat is losing heat continuously, say 4kW at 18 degrees.
So even though the boiler is more efficient by keeping to steady state, you are losing the heat at 3.5p x 4 = 14p per hour.


If you heat up the house several times a day, there will be a short period where it is not condensing when it starts up. So let us say in stop-start usage, you are losing 20% in efficiency at full power for one hour a day 3.5p x 20% x 30kW = 21p.


So, by not running the heating for 8 hours, you can save 14p x 8 = £1.12 , but you lose 21p on loss of efficency for one hour.

GlacialDrift

Thanks for the feedback everyone!

lollipopsarah

we've got ours on 16 - unless I can creeep it up to 17!
I assume you are all young and fit so why not wear an extra layer (hoody thing/dressing gown)
I may be wrong but I seem to remember that a good guide is to keep one room at 17 to prevent hypothermia?
It's all about try and error, when we first downsized we thought this flat was lovely and warm but now am not so sure, but then I could be just feeling my age - grrrrrrrrrrrrrr.
good luck
xx

terry2

Unfortunately, the correct answer is not straightforward, as it all depends on your property construction and insulation levels.
One thing that often gets forgotten is the point at which you feel comfortable.

If you live in a property that has brick/block inside walls and you have cavity wall insulation, then it is quite likely that it will be more energy efficient (ie cheaper) for you to have the CH on all the time. On the other hand if you have solid brick walls(ie no cavity), or light timber-frame internal wall construction then you will probably find it cheaper to have heating on only when you are present.

In the case with brick internal insulated walls, the points at which people feel comfortable are: burst heating at a high thermostat temperature, or continous heaing at a lower thermostat temperature. This is because while the walls are cold you need a higher air temperature to feel comfortable (think of it as all the walls acting as cold radiators to chill you). However if the walls are at room temperature you will feel comfortable with a much lower thermostat temperature. (note that it takes about 48hrs for the wall temperature to stabilize). The point is that it doesn't take very much of a lower temperature to offset the cost difference between burst and continuous heating.

sabretoothtigger

Reminds me of an old workmate, the condensation on his windows used to freeze solid on the inside. All depends what you are comfortable with, 15 and a jumper works for many on a budget.
Anything over 20 makes me sleepy personally

everach

I too have a similar issue with this.

We live in a new build house (about 8 years old), insulated external walls and loft. Internal walls, well i wouldnt lean on them too hard! haha.

I have had our heating on 16.5 set on constant but not sure if this is the right way to keep the costs down?

Also now im finding it a bit too chilly in the evenings,so give the electric fire a quick blast now n then to take the edge off, but then i thinK, ARRRGGHH the cost of that!!!

my partner is still in short sleeves, im in jumpers, boot slippers and scarf sometimes!

Guess the best thing to do is to take meter readings and see what happens!

bengasman

In essence, the answer is simple.
The more hours the heating is on, the more it will cost.
The higher you set your roomstat, the more it will cost.