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

Anthorn

richardc1983 wrote: »

What you're not understanding here is that its not on all the time full blast.

Another way to look at it is having a lightbulb on at 10% brightness 12 hours a day will use less energy than a lightbulb on at 100% 6 hours a day.

So therefore keeping the heating on low constantly is cheaper than it being off? I don't see the logic, sorry.

Marcio45

I have been reading this topic with interest and done myself a trial.
Background: we have a 1930's built three storey house with large windows, and it is cold, draughty. First it takes a while for the heating to be felt and once its off the temp drops quickly. We have a combi gas boiler and i monitored costs with my smart meter. Both experiements happened between 8am and 9pm, on days with similar temperatures outdoors.
First day: usually, i would set the boiler at its "supposed" efficient mode, where it heats up the water for the radiators at 73C. It warms up nice but once it reaches the 20C on the thermostat it switches off. In one hour it spends 70/80 pence on gas. So less than an hour after the house gets colder and it switches on again. Another 70/80 pences. In one day, i spent just over £5 on gas. And we could feel the quick drop in temperature in the house once the boiler switches off.
Second day: keeping the boiler on all day but reducing the boiler water output for 60C. As the day started the boiler was spending just over 40 pence an hour on gas but as the day progressed it came down to around 30 pence an hour. Besides the first couple of hours where the temperature indoors was not perfect, for the rest of the day it was very nice and confortable, temperature wise. We spent just under £5 on gas.
My conclusion is that on draughty houses like mine using high output on water temp from the boiler is a waste of money because the boiler works harder and once it is off the heat just disappears. Keeping it on all day, even with a lower heat setting, ends up spending the same but the confort is much better. It wont work the same for everyone, specially if a house is well insulated, but in my case it works better keeping it on all day from 8am till 9 pm.
Regards
Marc

richardc1983

Anthorn wrote: »

So therefore keeping the heating on low constantly is cheaper than it being off? I don't see the logic, sorry.

Yes if you reduce the flow temperature thus reducing gas usage...

Anthorn

richardc1983 wrote: »

Yes if you reduce the flow temperature thus reducing gas usage...

Looks like you're pretty much confused: If I leave my central heating on I'm paying for energy. But if I turn it off I'm not paying for energy.

But let's look at the operation of my central heating: The temperature set on the thermostat is not kept at a constant temperature. It is varied according to the weather: If I'm too warm I turn down the thermostat and if I'm too cold I turn up the thermostat. The alternative is to wear more layers of clothing when I get cold and remove layers of clothing when I'm too warm. That in itself completely debunks the idea that keeping the thermostat at a constant temperature provides more comfort. I quite simply doesn't!

But to recap; If I turn on the central heating it costs me money and if I turn off the central heating it doesn't cost me money. That's a matter of common sense. Ergo running the central heating for 6 hours a day is cheaper than running it 24/7. That too is common sense.

richardc1983

Anthorn wrote: »

Looks like you're pretty much confused: If I leave my central heating on I'm paying for energy. But if I turn it off I'm not paying for energy.

But let's look at the operation of my central heating: The temperature set on the thermostat is not kept at a constant temperature. It is varied according to the weather: If I'm too warm I turn down the thermostat and if I'm too cold I turn up the thermostat. The alternative is to wear more layers of clothing when I get cold and remove layers of clothing when I'm too warm. That in itself completely debunks the idea that keeping the thermostat at a constant temperature provides more comfort. I quite simply doesn't!

But to recap; If I turn on the central heating it costs me money and if I turn off the central heating it doesn't cost me money. That's a matter of common sense. Ergo running the central heating for 6 hours a day is cheaper than running it 24/7. That too is common sense.

No I am not confused I am actually a building manager and used to dealing with large scale heating and air con systems. Modern day BMS systems have been doing what opentherm does for years, they control the boiler flow temp for efficiency and to save on gas usage whilst keeping the building at comfort temp.

Your not getting it are you, I wonder if you are using a non opentherm boiler if so is it modulating and what do you have your flow temp at? Is it a condensing boiler. Try for a day running it the way you do currently at 6 hours a day and monitoring gas usage then the next day run it for 12 hours that day but once the boiler has brought the house upto temp then lower the flow temp on your boiler to say 40c and report back your gas usage, I think you'll be suprised.

Your talking like if you leave your heating on 24/7 it's either blasting away at full output and if you turn it off it's using nothing. Which would be the case on a non modulating boiler.

The way a modulating boiler works is like the lightbulb scenario I mentioned earlier. Another scenario is driving 100 miles at 70mph your going to use more gas because your going faster but the plus side of that is you get there quicker or you can use opentherm and once you've gotten half way the boiler will lower it's flow temp which means your speed comes down but your MPG goes up because your now going 50mph but it will take you longer to get there, once you get there the boiler modulates down even further and the gas/fuel you've saved from taking your time and going slower can be used to travel more miles or in boiler terms keep the heating on for longer which the non opentherm boiler used by going full pelt but getting there quicker.

For me it's cheaper to leave the heating on 24/7 with 21c comfort temp and 19c when were in bed. The thermostat keeps the house at this all the time. In the middle of the night the boiler will be running at minimum output with radiator flow temp of 30c this uses very little gas to keep that temp. I don't have to mess with my thermostat as it doesn't overshoot the temp set on the thermostat which anything over the temperature you want is wasted heat.

When we get up in the morning and ask for 21c the boiler may put the flow temp up to 45c for a short time then modulate back down. Last week's cold snap was the first time I had seen it go above 50c for a long time but the thermostat knows the outdoor conditions and compensates for this.

If I turned the heating off fully and the house dropped to say 12c the boiler would come on and produce a flow temp of 80c for several hours till it had pulled the temp up. By the time we leave the house it would be coming up to temp before it would go off.

This way we are always using gas but the rate of gas being burned is less than two timed periods a day with the heating being off completely in between. I've done the readings and monitored usage two years now and it is less this way for us as the boiler is just putting in a little bit of heat at a time rather than having to to full pelt.

It's also less wear and tear on the boiler from not going from one extreme to the other and you spend all of the time in condensing mode and the cooler your return the better as you get more efficieny and heat recovered from the waste exhaust fumes.

Anthorn

richardc1983 wrote: »

No I am not confused I am actually a building manager and used to dealing with large scale heating and air con systems. Modern day BMS systems have been doing what opentherm does for years, they control the boiler flow temp for efficiency and to save on gas usage whilst keeping the building at comfort temp.

Your not getting it are you, I wonder if you are using a non opentherm boiler if so is it modulating and what do you have your flow temp at? Is it a condensing boiler. Try for a day running it the way you do currently at 6 hours a day and monitoring gas usage then the next day run it for 12 hours that day but once the boiler has brought the house upto temp then lower the flow temp on your boiler to say 40c and report back your gas usage, I think you'll be suprised.

Your talking like if you leave your heating on 24/7 it's either blasting away at full output and if you turn it off it's using nothing. Which would be the case on a non modulating boiler.

The way a modulating boiler works is like the lightbulb scenario I mentioned earlier. Another scenario is driving 100 miles at 70mph your going to use more gas because your going faster but the plus side of that is you get there quicker or you can use opentherm and once you've gotten half way the boiler will lower it's flow temp which means your speed comes down but your MPG goes up because your now going 50mph but it will take you longer to get there, once you get there the boiler modulates down even further and the gas/fuel you've saved from taking your time and going slower can be used to travel more miles or in boiler terms keep the heating on for longer which the non opentherm boiler used by going full pelt but getting there quicker.

For me it's cheaper to leave the heating on 24/7 with 21c comfort temp and 19c when were in bed. The thermostat keeps the house at this all the time. In the middle of the night the boiler will be running at minimum output with radiator flow temp of 30c this uses very little gas to keep that temp. I don't have to mess with my thermostat as it doesn't overshoot the temp set on the thermostat which anything over the temperature you want is wasted heat.

When we get up in the morning and ask for 21c the boiler may put the flow temp up to 45c for a short time then modulate back down. Last week's cold snap was the first time I had seen it go above 50c for a long time but the thermostat knows the outdoor conditions and compensates for this.

If I turned the heating off fully and the house dropped to say 12c the boiler would come on and produce a flow temp of 80c for several hours till it had pulled the temp up. By the time we leave the house it would be coming up to temp before it would go off.

This way we are always using gas but the rate of gas being burned is less than two timed periods a day with the heating being off completely in between. I've done the readings and monitored usage two years now and it is less this way for us as the boiler is just putting in a little bit of heat at a time rather than having to to full pelt.

It's also less wear and tear on the boiler from not going from one extreme to the other and you spend all of the time in condensing mode and the cooler your return the better as you get more efficieny and heat recovered from the waste exhaust fumes.

No I have a Vaillant combi gas boiler ROFL.

Oh well, since you are a self-proclaimed industry professional what you say must be true then?

The fact remains that if I heat my property to whatever temperature when I'm not there it's costing me more money than if it's turned off.

As I posted earlier in this thread I have a thermostat in the lounge and thermostatically controlled radiators in other rooms such as bedrooms and bathrooms. That is the industry standard.

The fallacy that keeping the heating on low 24/7 is cheaper than a timer and thermostats has been debunked so many times that I hesitate to post links for fear of filling this post with links. But here is what I personally think is a balanced article from uSwitch:

However, if you leave your heating on 24/7, you will typically end up using more fuel. This is because some heat loss will always occur due to the difference between the temperature outside your house and the temperature you are trying to maintain on the inside.

Typically the most energy-efficient approach to heating your home is to programme your heating system so that it comes on when you need it most.

When you use your boiler timer and room thermostat in combination with radiator temperature controls (TRVs), you really do have the most energy-efficient approach to heating your home.

https://www.uswitch.com/energy-saving/guides/heating-on-all-the-time/

richardc1983

But I've done the maths, I save gas by letting it run low (19c) all day then on evening 21c.

As I've already stated this works for me and others are reporting the same. Do you not think the energy companies want you to use more gas so you give them more money. Not the first time these companies have given wrong advice.

You don't seem to understand the technology when that "industry standard" came out that was a long time ago we are now I'm a different phase of technology.

victor2

Winter after winter this saga rolls on...
While there may be circumstances where a finely tuned modern heating system in a house insulated to a high standard could have the heating on at a certain level(s) all day long, and not cost much more (or even less according to some "experts") than using the heating as required for personal comfort, how many consumers have and understand such environments to be able to take advantage of them?
I live in a 70s built estate and like a lot of residents have an old inefficient non-condensing boiler with a gravity fed hot water system. Changing to a condensing boiler would be very expensive and far outweight any cost savings made in energy usage over the life of the boiler. You can see the small number of houses that have condensing boilers when you see the boiler exhaust in operation.
Given that the average consumer IMHO has little idea what a kWh is, let alone how to make best use of their heating system, they would resort to the obvious conclusion that if your heating is on it is costing you money and if it isn't, it isn't.
My own experiments some years back confirmed the above. People who are interested in such costs should do their own experiments and reach their own conclusions - or just turn the heating on when they feel the need.

richardc1983

victor2 wrote: »

Winter after winter this saga rolls on...
While there may be circumstances where a finely tuned modern heating system in a house insulated to a high standard could have the heating on at a certain level(s) all day long, and not cost much more (or even less according to some "experts") than using the heating as required for personal comfort, how many consumers have and understand such environments to be able to take advantage of them?
I live in a 70s built estate and like a lot of residents have an old inefficient non-condensing boiler with a gravity fed hot water system. Changing to a condensing boiler would be very expensive and far outweight any cost savings made in energy usage over the life of the boiler. You can see the small number of houses that have condensing boilers when you see the boiler exhaust in operation.
Given that the average consumer IMHO has little idea what a kWh is, let alone how to make best use of their heating system, they would resort to the obvious conclusion that if your heating is on it is costing you money and if it isn't, it isn't.
My own experiments some years back confirmed the above. People who are interested in such costs should do their own experiments and reach their own conclusions - or just turn the heating on when they feel the need.

Quite right, its obviously going to be system specific but no one can deny that with the right setup energy/money can be saved if you run it efficiently.

Even your non condensing boiler if you reduce the flow temperature once comfort reached and then leave it running double the time you would normally have it running you may see savings.

System

Anthorn wrote: »

No I have a Vaillant combi gas boiler ROFL.

Oh well, since you are a self-proclaimed industry professional what you say must be true then?

The fact remains that if I heat my property to whatever temperature when I'm not there it's costing me more money than if it's turned off.

As I posted earlier in this thread I have a thermostat in the lounge and thermostatically controlled radiators in other rooms such as bedrooms and bathrooms. That is the industry standard.

The fallacy that keeping the heating on low 24/7 is cheaper than a timer and thermostats has been debunked so many times that I hesitate to post links for fear of filling this post with links. But here is what I personally think is a balanced article from uSwitch:



https://www.uswitch.com/energy-saving/guides/heating-on-all-the-time/

I bought this kit off EBay a couple of years ago for £30:

https://uk.eetgroup.com/i/NQ-9530-EU-NorthQ-Gas-Starter-Kit

It provides me with meter readings taken every 15 minutes. The Loop Energy monitor does the same thing. It takes the argument out of the argument. I know precisely how much gas is being consumed, and I can see that turning off the heating for a short period can result in higher gas usage than leaving it on. For example, when my CH first came on at 7am, 0.5m3/15mins was consumed. Now that the house is up to temperature, consumption has fallen to 0.1m3/15mins. I do turn down my CH set temperature overnight.