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

grahamc2003

jeepjunkie wrote: »

Yes I did pay that invoice. It is simply connected to existing tank/rads and is working well.

Regards the other amount yes an EcoDan was within that price but was the total amount for a huge amount of renovation work.

Out of date/misleading posts are removed to avoid confusion. When doing research what annoys me is results full of out of date info. So I do the courtesy...

I can give some up to date info on ashp costs, with the latest quote yesterday.

14kW Ecodan, £10.5k (includes new tank, and all work, plus another 3 grand for wet system

15kW Dimplex, £9k, ditto

14kW Ecodan, £10k, lowered to £9.5k due to other quotes.

Also got a quote for a rhi qualifying wood burner, was around £1.6k, since rhi £3.5k, ex fitting or anything else.

Appreciate a PM if you know anyone who could quote £5k for the above!

wantanswers

oldskoo1 wrote: »

Anyone who has tested the 24/7 theory recently when the temperatures have been a bit higher around the 7-10c mark might get a shock when their bill arrives if we have prolonged periods of minus or close to freezing temperatures.

The difference in cost is more apparent when the outside temperature is lower.

To be fair oldskoo1, when outside temperatures are forecast around 7 - 10c I wouldn't even consider testing the theory. But also to be fair i'm seriously looking at installing pre programmable "night set back" facilities, mainly for cold weather as of recent!

Cardew

oldskoo1 wrote: »

Anyone who has tested the 24/7 theory recently when the temperatures have been a bit higher around the 7-10c mark might get a shock when their bill arrives if we have prolonged periods of minus or close to freezing temperatures.

The difference in cost is more apparent when the outside temperature is lower.

Also when making comparisons, people need to factor in the fact that a house is a huge heat sink.

A house heated to an average of, say, 20C might only drop to 16C overnight. Therefore to bring it up to 17C will require little energy.

grahamc2003

Not sure why people aren't using like-for-like comparisons for the subject of this thread. I doubt any would argue that if you set a higher temperature when you turn it on and off, it could work out cheaper to leave it on all the time at a lower temperature. It's not really a valid argument, is it, and it doesn't make the myth a reality.

Surely no one can seriously argue that if you wife/cat/parrot somehow turns the temperature right up when used intermittantly, but doesn't if it's on constantly 'proves' the myth.

If you don't compare like with like, then you might as well say the Queen turns Buck Palace heating on and off, and she pays £2,000 per week, I keep mine on all the time and pay £100, therefore it's not a myth!

The key is to understand the statement 'all other things being equal' - i.e. heating is more expensive if on all the time rather than being turned on and off as necessary, all other things being equal.

If they are not equal, say you set the temp to 0C when you have it on all the time, and 30C when on and off, then you can't say it will be cheaper (and no one has, the implication is a o t b e).

Also, arguments like 'it's more expensive to turn it on and off because my mate had a burst pipe when it was off, so you have to add £800 to the on/off costs.' and similar aren't relevant.


No one is saying turn you CH on and off. All that is being said is that it is cheaper to turn it on and off. If people want it warm all the time, then fine, keep the heating on all the time. No probs, except when most who do perversly want to re-write the laws of physics for some reason by saying its cheaper to do so.

I must say, of all the threads I've seen on mse, this has been the most surprising (which is quite a statement).

macman

My living room is currently at 19C (as set on the room stat).
So I'm officially at risk of death now!
Who do I call?
And can I get compensation?

grahamc2003

macman wrote: »

My living room is currently at 19C (as set on the room stat).
So I'm officially at risk of death now!
Who do I call?
And can I get compensation?

Quick! Turn it up and save a bit of money! Save more by leaving it on all night!

HappyMJ

oldskoo1 wrote: »

Anyone who has tested the 24/7 theory recently when the temperatures have been a bit higher around the 7-10c mark might get a shock when their bill arrives if we have prolonged periods of minus or close to freezing temperatures.

The difference in cost is more apparent when the outside temperature is lower.

How much of a shock? All I see on this thread is two opposite sides. One where posters are claiming having the heating on one third of a day (8 hours) will cost one third as much as 24 hours and the other claiming that having it on from 8-4 (whilst at work) instead of off will only cost 5% more....so which is it?

If I kept the heating on a comfortable level 24 hours 7 days then yes it would cost more than keeping it set to 21 degrees for 2 hours in the morning and 6 hours in the evening (and using the thermostat to set it to 16 overnight) and all weekend but the difference isn't shocking. It isn't 5% but it's not shocking neither. We are only talking about the timer turning it off during the day when no one is at home when the heat loss isn't that much anyway. I would assume most people in the UK would keep the central heating on but set to a lower temperature overnight just in case the house gets too cold it'll come on and top it up. If i turned the heating off overnight then I'm sorry but it gets too cold so I turn it down instead. So in house - heating on...out of house - heating off. But if I go out and forget to turn the heating down such as on a weekend when the timer does not turn it off then the difference isn't shocking it just costs a little more.

If I were to have a guess then as the boiler in my house uses 14.65kW and when at the set temperature the boiler comes on about 20% of the time to maintain the temperature during the day then over 8 hours it would use 23kWh per day. If the heating had been off during the 8 hours then it would come on and reheat the house back to 21 degrees from what it fell to would probably would have been about 14 or so (1 degree per hour my house doesn't cool quickly) which would take about half an hour using 7kWh. So an extra 16kWh per day of heat is effectively wasted. 5 days a week means it would use an extra 80kWh per week. 39 weeks of heating in a year means an extra 3,120kWh per year. At 3.5p/kWh that would be £109 per year. It's not a shocking amount. As most customers are on direct debit leaving the heating on all day adds about £9 to a monthly direct debit the average of which is now about £110 per month.

grahamc2003

HappyMJ wrote: »

How much of a shock? All I see on this thread is two opposite sides. One where posters are claiming having the heating on one third of a day (8 hours) will cost one third as much as 24 hours .

I've read the whole thread and haven't seen anyone saying that!

Could you post a link?

Cardew

jeepjunkie wrote: »

Yes I did pay that invoice. It is simply connected to existing tank/rads and is working well.

Well an Ecodan ASHP wouldn't normally be able to work with existing radiators as the water temperatures are too low.

However not everyone contemplating an ASHP would have had to foresight/luck to have an 'existing' LPG CH system with 13 fan convectors and underfloor heating in the bathroom.;)

Our ASHP heats and does DHW through 1 towel rail rad, 13 fan convectors and ufh in
the bathroom 24/7

wantanswers

grahamc2003 wrote: »

Quick! Turn it up and save a bit of money! Save more by leaving it on all night!

Be sensible graham2003.

Look the temperatures for the next five days (day and night) are going to be hovering around zero and it may be more cost effective to keep your heating on 24/7 albeit maybe turning it down later at night until morning.

No one is trying to re write the laws of physics!