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?

[MistyBean]

I agree about not having blind acceptance over novel and complex issues, but this is basic science. I just get frustrated at how much the basics get questioned these days and how no one values expert opinion.

[cakeorwine]

@Cigent

That's an excellent idea. I'm going to do that.

Assuming on day 1, it's 10 c outside and day 2, it's 4 degrees outside

If you tried to maintain the heating at 20 c, you would use more energy on the colder day.

That's why heating bills are highest on the coldest days.

If you set it at 17 c, and the temperature was 10 C on 1 day and 4c the next day, you would use less energy than setting at at 20C and you would use more energy on the colder day.

[cakeorwine]

On a colder day, you get colder than on a warmer day. As your body loses heat quicker.

You can insulate yourself but you use more energy to keep yourself warm.

If you want to keep yourself at a lower temperature, you would use less energy.

And on a hot day, well - you can actually over heat.

[Cigent]

@FinanceLPlates

This is why insulation matters! If your house were perfectly insulated it would stay at 20 degrees. Most U.K. houses are very “leaky”. So when the outside temperature is lower your boiler has to keep working hard to maintain 20 degrees inside, as it’s constantly replacing lost heat/energy. Keeping it to 17 degrees uses less power as the temperature difference isn’t as high.
Of course with proper insulation you’d be warm and use less energy…

I've had a look and my house is rated C with 'the potential to be C', with everything considered 'good' or 'very good'. So maybe it won't lose too much heat if I keep it on 20. Worth an experiment anyway.

[ValerieDoonican]

Think of your house as a veey tall glass with a small hole at the bottom. Imagine the bottom of the glass is the average outside temperature in January 8 degrees. About 3/4 of the way up the glass draw a line called "17", at the top, another line called "20".

If you fill the glass up to 17 the water won't leak out if the little hole as much as if you fill to the top (20), because there is less pressure.

Your job is to run to the tap with a thimble (b/c water is expensive so you have to do a lot of work to get it) tip it into the glass and then run back for another one, trying to fill the glass faster than the water runs out. The fuller the glass, the faster it leaks out, the faster you have to run with your thimble.

Even when youve filled the glass (warmed up the house) you have to keep going backwards and forwards to replace what leaks out. At 20 you have to go backwards and forwards rather more often, as the higher pressure means the leak is faster.

Pro tip: insulating your house is the equivalent of making the hole in the glass smaller.

[TinySaltLick]

Newton solved this a while ago:

Newton's law of cooling states that the rate of heat loss of a body is directly proportional to the difference in the temperatures between the body and its environment.

en.m.wikipedia.org/wiki/Newton%27s_law_of_cooling

Your house is constantly losing heat if it is colder outside. The greater the temperature difference the quicker it cools down. The error in your logic is the comparison from 19 to 20 to 16 to 17. In the former it is losing heat quicker - so not only will it take longer to raise 1 degree, it will cool 1 degree faster

[cakeorwine]

I've had a look and my house is rated C with 'the potential to be C', with everything considered 'good' or 'very good'. So maybe it won't lose too much heat if I keep it on 20. Worth an experiment anyway

But it will still cost more energy to get it to that temperature.

It uses more energy to make something warmer.

Your house will lose heat.

Experiment if you will...but you can't change the laws of thermodynamics

[EducatingArti]

@Cigent

I've had a look and my house is rated C with 'the potential to be C', with everything considered 'good' or 'very good'. So maybe it won't lose too much heat if I keep it on 20. Worth an experiment anyway.

You will still lose heat more rapidly and need the heating on more to keep it at 20 degrees than at 17.
I don't think C insulation rating is anywhere near 100% ( and actual 100% insulation would be impossible to achieve anyway).

[FTHC]

If you set it at 20° everytime it drops below 20° in your house, the boiler will kick in using gas to maintain the temperature at 20°.

If you set it at 17° it will do the same to maintain that temperature but it's not as likely to drop below 17° as often as it is to drop below 20°, so you won't use as much gas keeping the house heated to 17°.

[EducatingArti]

@MistyBean

I agree about not having blind acceptance over novel and complex issues, but this is basic science. I just get frustrated at how much the basics get questioned these days and how no one values expert opinion.

I am also rather sad about this!

[TinySaltLick]

@FinanceLPlates

This is why insulation matters! If your house were perfectly insulated it would stay at 20 degrees. Most U.K. houses are very “leaky”. So when the outside temperature is lower your boiler has to keep working hard to maintain 20 degrees inside, as it’s constantly replacing lost heat/energy. Keeping it to 17 degrees uses less power as the temperature difference isn’t as high.
Of course with proper insulation you’d be warm and use less energy…

This isn't correct. If your house was perfectly insulated, it would still be exactly the same temperature as outside if you had nothing emitting heat inside. It just slows down the loss of energy via heat loss.

The rest of the logic makes sense minus this erroneous statement

[Cigent]

@cakeorwine

I've had a look and my house is rated C with 'the potential to be C', with everything considered 'good' or 'very good'. So maybe it won't lose too much heat if I keep it on 20. Worth an experiment anyway

But it will still cost more energy to get it to that temperature.

It uses more energy to make something warmer.

Your house will lose heat.

Experiment if you will...but you can't change the laws of thermodynamics

Worth an experiment to see what the financial difference is between 17 and 20, I meant. I know it will lose heat.

[cakeorwine]

Worth an experiment to see what the financial difference is between 17 and 20, I meant. I know it will lose heat

Lots of variables to control for.

Turning down the heating does save you money - and with energy at an expensive price, it will add up.

[watingroom2]

I do not think the temperature is the same in all houses - in some houses (low ceilings good insulation) 18 degrees would feel far warmer than in other houses (high ceilings - single glazing - poor insulation) :

[TooMuchToDoTooLittleInclination]

@HarpicHarpy

Damn. I was with the op until the rest of you rocked up with your common sense.

🤣🤣🤣

[ConfusedBear]

You cannot see a temperature difference of a few degrees with your eyes so it is difficult to visualise how heat leaks out of a house.

Imagine you were trying (for some reason) to fill a shopping bag with water and it was leaking out along all the seams. The more full you tried to have the bag, the more side seams available for water to leak out along. So the higher the water level the more water you would need to add to the bag to replace what is being lost. This is because the water wants to find the lowest point and be as flat as possible.

Heat works in a similar way, it wants to flow from hot things to colder things. The bigger the temperature difference between the hot and cold thing the bigger the heat flow between them and the more you need to top up the heat in your house. This uses more energy and so costs more.

Hopefully this is useful - ignore the post if it makes things more confusing.

[Pootle40]

@FTHC

If you set it at 20° everytime it drops below 20° in your house, the boiler will kick in using gas to maintain the temperature at 20°.

If you set it at 17° it will do the same to maintain that temperature but it's not as likely to drop below 17° as often as it is to drop below 20°, so you won't use as much gas keeping the house heated to 17°.

THIS. It will click on much more to maintain 20c than 17c.

[lightisnotwhite]

@FinanceLPlates

This is why insulation matters! If your house were perfectly insulated it would stay at 20 degrees. Most U.K. houses are very “leaky”. So when the outside temperature is lower your boiler has to keep working hard to maintain 20 degrees inside, as it’s constantly replacing lost heat/energy. Keeping it to 17 degrees uses less power as the temperature difference isn’t as high.
Of course with proper insulation you’d be warm and use less energy…

This is the bit I can’t understand as everyone says keeping your windows in winter is good, let’s in the fresh air, stops condensation etc. Yet that completely defies the point if insulating to my mind.

[FinanceLPlates]

@TinySaltLick

This isn't correct. If your house was perfectly insulated, it would still be exactly the same temperature as outside if you had nothing emitting heat inside. It just slows down the loss of energy via heat loss.

The rest of the logic makes sense minus this erroneous statement

OP says “… once it’s at 20 degrees”. So yes, of course she’ll need to get it to that temperature first, but that wasn’t her question.

The question was why does it cost more to maintain a temperature of 20 vs 17 degrees.

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

[Summerfun54321]

Your heating isn’t the only thing that heats the house. Even without the heating on its generally warmer inside than it is outside due to humans giving off heat, appliances such as cookers giving off heat and sunlight. These are called “internal heat gains” and “solar heat gains”. The job of heating i.e a boiler is to simply top up these internal and solar gains to reach a target indoor temperature (set at your thermostat). The lower the target indoor temperature, the more likely the internal and solar gains alone will be sufficient to meet this target temperature without the need for heating at all.

[cakeorwine]

@lightisnotwhite

This is the bit I can’t understand as everyone says keeping your windows in winter is good, let’s in the fresh air, stops condensation etc. Yet that completely defies the point if insulating to my mind.

Your house does need to breathe as well - moisture builds up as does the effect of having humans in a house.

Fresh air is good - but it does let the heat out.

[Boreded]

Do people really leave their heating on overnight? I just noticed a few replies that seemed to be saying they do. mine is set to off (which is actually 5 degrees to stop pipes freezing) but never comes on. isn’t the point of duvets so that we don’t need night time heating?

[Dexionmagic]

Basically….. the hotter you want your house the more it will cost.

If you have decent/lots of insulation then heat loss will be less but my first statement still applies.

The greater the difference between interior temperature and exterior temperature the more the heating will be on and burning gas/oil etc. Insulation will lessen the fuel burnt but the first statement still applies.

[BloodyCamping]

Read through this article. Basically one fegree higher increases your heating bill by 10%

www.which.co.uk/reviews/boilers/article/tips-to-reduce-your-heating-bills-aqik36F56DvJ?source_code=911CRJ&&source_code=911CRJ&gclid=Cj0KCQjwjvaYBhDlARIsAO8PkE1xFVs4FhvnY_MY1hMdU3qcPdlv7JuSvjOUwbYNiPFRpWbUNiEikKYaArKrEALw_wcB&gclsrc=aw.ds

[TiredButDancing]

It might be easier to visualise if you swap it round. Imagine you have an ice block which you take out of the freezer and leave on a plate. You need the ice block to be on the plate but you can't let it melt. So as soon as it starts melting, you have to put it back in the freezer for a bit.

If its a hot day, you are going to be constantly running back and forth to the freezer. And thr hotter it is, the more this is true and in fact, you probably can't maintain your ice block. If its a cool day, your ice block Will melt much slower and you will have plenty of time to refreeze it.

It's the same with heating, but in reverse. So keeping the house at 20 when it's mild out probably won't be that difficult. But when it's properly cold, your heating will need to constantly come on and work to maintain the temperature. Which of course then costs more.