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

Danny30

Our heating is left all the time on thermostat but when it goes from 17 degrees to 20 degrees in the morning, I notice a big spike, particularly in the first hour, or two.

Is there any consensus on whether it uses less gas to have the flow temp higher with the home quicker to heat up to the required temperature, or to lower the flow temp in which case it takes longer for the house to heat up.

richardc1983

Danny30 said:

Our heating is left all the time on thermostat but when it goes from 17 degrees to 20 degrees in the morning, I notice a big spike, particularly in the first hour, or two.

Is there any consensus on whether it uses less gas to have the flow temp higher with the home quicker to heat up to the required temperature, or to lower the flow temp in which case it takes longer for the house to heat up.

Look at this video: https://www.youtube.com/watch?v=kGs_biFA87Q 

Your home isn't just about the air temperature it's about the fabric of the building, when you have the flow temp set higher, the air temp may come to temperature quickly leading to the room feeling hot or stuffy but the fabric of the building and all the furniture needs to absorb the heat to come up to the same temperature, this happens slowly. 

https://www.heatgeek.com/should-your-heating-be-left-on-all-the-time-or-not/ 

First of all, ‘leaving your heating on all the time’, often is a misunderstanding.  It does not mean set your thermostat to say 21°C permanently.  It means making use of ‘setback’ temperatures. 

It's a bit like saying, I'm going to drive 100mph to the shops as I'll only be driving for 30 seconds.  Actually, if you drive at 5 mph you will take 3 mins, it may ‘take longer’ but it will be much more efficient with fuel.

Ultrasonic

richardc1983 said:

It's a bit like saying, I'm going to drive 100mph to the shops as I'll only be driving for 30 seconds.  Actually, if you drive at 5 mph you will take 3 mins, it may ‘take longer’ but it will be much more efficient with fuel.

Driving at 5 mph wouldn't be efficient at all but that's a rather different subject  .

@Danny30 there isn't a simple consensus as there are a lot of variables here. Take the article at the very start of this thread as a counter-example to the views being expressed by @richardc1983 . The important complicating factor is heat loss, which is reduced as your house cools down. Very efficiently generating heat that is then mostly lost without significant benefit is not going to save energy overall. I suspect that what ultimately saves the most energy will therefore depend on how long and how low temperatures drop in each area of the house.

Yesterday I was out of the house for work from about 9:30 till 19:00, and by only having the heating on after I got home in the evening my total gas use for the day was just over 10 kWh (including a shower heated using my combi boiler). I'm in no way suggesting this is a model applicable to most but giving an example of a very focused energy use approach as opposed to aiming for maintaining particular minimum temperatures with constant slow heating. The thermostat in my lounge was showing the temperature was 14°C when I got home FWIW.

When weighing up different options I think it's important to be mindful of how small the efficiency differences discussed above were.

Spies

Dropped my flow temp to 60c but increased my setback to 16c instead of 14c, lets see what happens. 

BUFF

Danny30 said:

Our heating is left all the time on thermostat but when it goes from 17 degrees to 20 degrees in the morning, I notice a big spike, particularly in the first hour, or two.

Most modern boilers on first firing up will go to full power for a while before then starting to modulate down to demand. The higher/longer the difference between the actual temp. & the desired set temp. demand then the longer before the boiler will start to modulate.

Danny30 said:

Is there any consensus on whether it uses less gas to have the flow temp higher with the home quicker to heat up to the required temperature, or to lower the flow temp in which case it takes longer for the house to heat up.

This comes down to the fabric of your building (i.e. an older "thermal mass" type building or a more modern highly insulated build) & your heating system/controls. However, your preferences for comfort/convenience v minimum cost & how you inhabit the building (out for work all day, in all day or somewhere in between) will also come into your decision.
Differences are likely to be of the order of 5-8% so unless you have 2 identical days weatherwise to compare running both ways then even minor differences in weather could hide any savings/additional cost.

Ultrasonic

richardc1983 said:
Look at this video: https://www.youtube.com/watch?v=kGs_biFA87Q 

Having watched that video it was actually more balanced than I was expecting, and doesn't present a 'low and slow is best for everyone' line that many may think.

anon_ymous

Ultrasonic said:

richardc1983 said:
Look at this video: https://www.youtube.com/watch?v=kGs_biFA87Q 

Having watched that video it was actually more balanced than I was expecting, and doesn't present a 'low and slow is best for everyone' line that many may think.

I've read that keeping the heating on at a certain temp is recommended ONLY if you have decent insulation?

Ultrasonic

waqasahmed said:

Ultrasonic said:

richardc1983 said:
Look at this video: https://www.youtube.com/watch?v=kGs_biFA87Q 

Having watched that video it was actually more balanced than I was expecting, and doesn't present a 'low and slow is best for everyone' line that many may think.

I've read that keeping the heating on at a certain temp is recommended ONLY if you have decent insulation?

I'd suggest you watch the video.

(Keeping the same temperature 24/7 makes sense for pretty much nobody though, since at a minimum a lower temperature at night makes sense.) 

richardc1983

Ultrasonic said:

waqasahmed said:

Ultrasonic said:

richardc1983 said:
Look at this video: https://www.youtube.com/watch?v=kGs_biFA87Q 

Having watched that video it was actually more balanced than I was expecting, and doesn't present a 'low and slow is best for everyone' line that many may think.

I've read that keeping the heating on at a certain temp is recommended ONLY if you have decent insulation?

I'd suggest you watch the video.

(Keeping the same temperature 24/7 makes sense for pretty much nobody though, since at a minimum a lower temperature at night makes sense.) 

Agreed, if you also have  a property with high thermal mass it acts as a heat sink too. I posted a few replies back leaving it on 24/7 doesn't mean a fixed temp 24/7 although you may find you never need to increase your night set back temp.

anon_ymous

Ultrasonic said:

waqasahmed said:

Ultrasonic said:

richardc1983 said:
Look at this video: https://www.youtube.com/watch?v=kGs_biFA87Q 

Having watched that video it was actually more balanced than I was expecting, and doesn't present a 'low and slow is best for everyone' line that many may think.

I've read that keeping the heating on at a certain temp is recommended ONLY if you have decent insulation?

I'd suggest you watch the video.

(Keeping the same temperature 24/7 makes sense for pretty much nobody though, since at a minimum a lower temperature at night makes sense.) 

Thanks. I've watched that, and now even more confused In my parents house, they use gas where they only put heating on when needed

So you should perhaps leave it on x amount, but based on a timer? Or always leave it on, at least 16C? ALso, I personally get v warm at night anyway