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?

It really depends where you live and how your house is built though.

Try to imagine, if you can, that not everyone lives in your house, your street, or even in the same city as you. It's hard. I know.

I think it's not that 19 to 20 is more than 17 to 18

But that 19 to 20 will occur more often than 17 to 18 because the heat loss will be faster if it 20 to 10 outside than 18 to 10'outside

I am visualising that as a pressure difference - the heat loss is faster if the difference is bigger ?

That's a lot of scienceplaining going on there.....

😂😂

Maybe we need our credentials at the bottom of each post to make sure we don't fall foul of 'splaining' anything in future.

If you think about a cup of tea, it gets from burning hot to drinkable quite quickly, stays drinkable quite a while, and lukewarm for ages.

That's because, just as so many have explained, the greater the difference, the quicker the heat loss - it's like curve where the big difference means heat is dumped quickly, then the middle bit it's quite slow, then as the temperatures approach each other it gets slower and slower until they eventually match.

So even though it's only one degree difference in both cases, you'll have to boost the heat more often at 20 because it cools down faster.

Personally the first change I'd make is turning it off at night though - who needs to heat the house when you're all tucked up in bed!

Because the temperature gradient isn't 20-19 or 17-16, it's the internal to external temperature. So if your external temperature is eg 14 degrees, your temperature gradient is 20-14 vs 17-14. Hence cooling more quickly.

Not a thermal engineer but I spend a lot of my working life cooling down people and warming them up again!

Thanks and apologies as I've not read the whole thread!

The tea example makes sense as room temperature is about 20 degrees. Therefore the delta T is largest, say 80 degrees (assuming boiling water is 100).

I guess what you're saying is that heat loss is exponential and not linear, which makes sense. However, do you know where this temperature scenario would lie on a heat loss curve, for a typical house in the UK?

I'm assuming this would be the critical aspect as the cost would be highly dependent on this.

Errrr..... OP hopefully you've woken this morning and realised the answer is obvious. Now go turn that thermostat to 18 and save yourself some money

Sorry, I thought the external temp would be 19 and the internal 20. Thus a 1 degree delta.

Likewise for the 18-17 case, a 1 degree delta.

Good lord. I've said I must be wrong, that I'm wrong, and thanks everyone for their explanations.

The irony of not reading something properly in a desperate rush to criticise someone for not understanding something properly.

I don't suppose it occurred to you that not everyone lives in your town, and other people may live somewhere that is colder than where you live?

@Lunar270

1 degree is 1 degree

But you need that 1 degree heating more often if it's lost quicker which happens if the difference between outside and in is larger

and not everyone is you. I have my mother living with me. She is a disabled wheelchair user. She cannot move more to keep warm and I just can’t walk extra layers on her as wearing anything bulky limits what little mobility she has. She feels the cold pretty much all year round so wears the same regardless of it being summer or winter so whilst I am still sitting here in shorts and t shirt without socks my mum is wearing a nighty under a fleece dress with slippers and a heated throw. By October the heating will be on 24/7 set at 20 as she doesn’t sleep like a younger person. She doses in her chair on and off all day and night so doesn’t actually go to bed as she can’t lie down. She might be awake at 2 in the morning watching telly and going backwards and forwards to the loo and she has bowel and incontinence problems hence my heating on in the areas she uses.

Whoops should have quoted Ratherperplexed not Longlivedqueen so my apologies to her

This thread makes me think it would be a good idea if schools introduced science as a subject

Yes, 1° is 1° but a PP has said that cooling from 20° to 19° will happen more quickly than cooling from 18° to 17°.

I appreciate the frequency at which you change that 1° is important but that isn't what I was asking.

Perhaps English too.

😂 the issue isn't whether it's taught but how much of it sinks in, or what you do for a career.

I work with lots of thermal engineers but wasn't interested, other than for what I do as a mech eng. It wasn't immediately obvious to me that cooling was exponential and not linear.

Indeed.

@Ratherperplexed well if people in your house are wandering about naked in October with no heating on, it's not surprising if they're cold.

it still amuses me that people have rigid dates that determine their heating. It's bizarre.

you can put extra layers on in Nov/Dec etc to be warm enough without putting the heat on/higher and you can put the heating on before half term is extra layers aren't enough. The date has NO affect on the temperature.

The date has NO affect on the temperature.

Yes, I think people are aware of that 🤣

But most households can't afford to have the heating on regularly for months at a time so having a start date of (say) November means they aren't spending a fortune on gas bills.

It'll save a bit, not loads and it'll depend on where your thermostat is and if that room is shut off from the rest of the house efficiently. If the air is circulating around the house it will save much less than if the air is unable to escape.

Generally that would be right, but it will depend where your thermostat is.

I know I sound like a broken record, but it's something a lot of people don't take into consideration.

same with when they say what temperature they keep the house at. People may need to picture the extremes of that for it to really make sense. If the thermostat was in a cupboard under the stairs that had a radiator and set to 20° Opposed to in the porch set to 20° Your lounge would be very different temperatures.

I don't have to understand exactly how a process works to know that the weight of science is behind it.

I am expert in some things, then for other things I trust other experts. The key is choosing carefully who to listen to.

Well that's a worthwhile contribution to the thread

At 20 in most places (assuming you’re UK), it will keep going on and off. Heating up is more costly than keeping at a constant I think.