To think keeping thermostat at 20 will cost the same as keeping it at 17?

[Cigent]

I know it's said that turning the heating down a few degrees will save money, but how?

If I'm, say, October I set the heating to 20 degrees and leave it like that, and if it falls to 19 degrees it automatically kicks in until the house is up to 20 then switches off, how would that cost any more than keeping it at 17 and it kicking in when it dropped to 16 to heat the house one degree? In both cases it's only kicking in to heat the house by one degree, so how does keeping it lower cost less money?

I understand that if I turn it on when the house is at, say 15 degrees, then it would cost more to get to 20 than 17, but once it's there surely it would be the same to keep it there?

24 hours every day for the past week really..

@Cigent Take two hot water bottles. Fill them both with hot water from the kettle (100 degrees) and then leave one on the kitchen counter (20 degrees), and put the other one in the garden (0 degrees).

The one in the garden is going to get colder a lot quicker, because there's a bigger temperature differential. 100 degree difference for the one outside compared to an 80 degree difference inside

Heating a house is exactly the same, except that the consistent temperature is the outside temperature. If you've got 2 identical houses, one with the heating on at 17, and one at 20, then the one at 20 has the bigger temperature differential, so will lose heat more quickly.

So while the 17 degree house may lose 3 degrees every 2 hours, the 20 degree one might lose it in 90 minutes, which would mean for every £1 the 17 degree house spends on energy, the 20 degree house spends £1.33

(Disclaimer, the numbers are all pulled out of my arse as an example, I have no idea the actual cost difference.)

Bugger, just spotted this is a zombie thread. Bloody bollocking mumsnet similar threads thing.

@lottielooinwonderland you need to think about heating yourself, not the space. So turn it down in the day and use layers, wrist warmers, hot water bottles/heat packs and hot drinks to keep you warm.

Have you got curtains or secondary glazing to reduce the heat loss through your windows? It will be costing a lot, if it's constantly kicking in and out.

yup this is the one - also all houses are ventilated to some extent and cold air will come in from outside on a regular basis, e.g. using the front door, say for the sake of argument the outside air is 2 degrees, heating it to 17 degrees will take less energy that heating it to 20 degrees.

Lowering the thermostat will therefore lower the overall heating bill, as would using things like draft excluders and double/triple glazing.

@FinanceLPlates

For temperature maintenance (hot or cold) insulation makes all the difference, as it makes you independent from the outside temperature.

No insulation is 100% efficient... its a physical impossibility, so you can never be independent of the outside temperature.