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

Cardew

Hengus wrote: »

I am not out to prove a point. My CH is ON overnight but I accept that it is set to a lower temperature of 16C.

I am firmly in the 'have your heating timed' camp.



That said I too have my CH on 24/7 albeit, like you, set back to 16C overnight. In my case setting it at 16C means the CH is effectively 'off' as it would be very rare for the temperature to drop that low from the usual evening internal temperature of 21C.


So running heating 24/7 with temperature set back at night is effectively timed!!



I have a converted detached stables as an annex which is rarely used. It is close to 200 years old, non-cavity walls(albeit dry lined) but fully central heated with a modern combi boiler. When it is unoccupied - which is most of the winter except Xmas - The CH is set to come on at 3C(frost stat) and there is absolutely no damp. I have been running it like this for 30 years even with the old non-condensing Combi. It would be interesting to hear from some of the 'experts' on this thread how I should set the CH to save money;).

richardc1983

Cardew, of course running it at 3c all the time when unoccupied is going to be cheaper than when not running it.

I think the time is relative to occupied time vs unoccupied.

Anthorn

Cardew wrote: »

I am firmly in the 'have your heating timed' camp.



That said I too have my CH on 24/7 albeit, like you, set back to 16C overnight. In my case setting it at 16C means the CH is effectively 'off' as it would be very rare for the temperature to drop that low from the usual evening internal temperature of 21C.


So running heating 24/7 with temperature set back at night is effectively timed!!

But if the heating is "effectively 'off' as it would be very rare for the temperature to drop that low from the usual evening internal temperature of 21C" (QUOTE) it's not on 24/7.

richardc1983

Anthorn wrote: »

But if the heating is "effectively 'off' as it would be very rare for the temperature to drop that low from the usual evening internal temperature of 21C" (QUOTE) it's not on 24/7.

My word Anthorn you argue with everyone!

malc_b

To answer a question so far back I've lost it, yes, better insulation means less over all energy loss per day but as a percentage a higher loss when the heating is off because the temperature inside the house doesn't fall as much.


The best analogy I think is driving a car. We all know the fast you drive the more fuel you use. But equally you don't drive at 10mph because that is inefficient too. Usually 50mph is the best speed, just into the highest gear. Heating a house is similar. Whack the boiler up to max and you won't be condensing so you'll lose 5-10% on efficiency. Have the heating on 24hr and you increase the heat loss during what was the off time as temperature will be higher. That will cost you about 5%. The optimum is like driving 100miles in exact 2hrs at 50mph. The boiler has to run in condensing mode all the time and is only on for just enough time so that when you are home the house is at your comfort figures.


In other words as the weather gets cold the heating starts earlier so that it never needs to exceed 55C return water temperature.


BTW there is a simple way to estimate your heat loss percentage. Buy yourself an internal/external thermometer or maybe just go on what the weatherman says and an internal. When it is cold outside (0C ideally as that is the usually design figure). Turn the heating off at bed time and note the temperature. Leave the heating off until morning. Note temperature and then turn it on.


Let's say it was 20C at bedtime, 16C in the morning, and 0C outside. Heat loss as a pensioner has stated depends on the temperature difference. Hence we have 20x at bedtime, 16x at breakfast. Call that 18x average (and yes this introduces a small error as it is a curve). If we kept the heating on all night then it would be 20C at bedtime, 20C at breakfast 20x would be the heatloss. So we saved 2x or 10% of the heat overnight. If we say bedtime to breakfast is 8hrs and we are then going to heat for the remaining 16hrs in the day then the saving for the day is 3.3%. That is a day is 20x + 20x + 18x rather than 20x + 20x + 20x.


So the cold your house is in the morning the more you save by turning the heat off. The warmer it is, i.e. the better insulated it is, the less you save in percentage terms by turning the heat off.

Paton147

I spotted this 51 page thread and have had a good old chuckle at it!

We have a relatively big, drafty Victorian house yet we only schedule a few bursts of heating throughout day. Supposing it’s a very cold night, the chill is eliminated within 10 minutes of the heating kicking in at 7am and the house is cozy within 15-20 minutes.

If you think about it rationally, For energy to be expended economically it is done so irregular in response to varying conditions/forces. When you work out, energy levels peak and trough. When you drive a car, your foot isn’t constantly on the accelerator regardless of gradient.

If you want to go through winter without your property dropping below a temp you deem cozy then by all means have the heating run 6am till 10pm every day. You’re paying a premium for it though.

If you want to dramatically reduce your consumption then accept that from time to time you’ll need to stick the heating on out with you schedule. Your body, clothes and furnishings all retain heat so it’s not a big deal if the air temp drops a few degrees in the hour before you go to bed anyway. Having the thermostat compensating for that when your concious of your bills is madness.

The thermostat works exclusively on air temp... not you warm you actually are...

richardc1983

Paton147 wrote: »

We have a relatively big, drafty Victorian house yet we only schedule a few bursts of heating throughout day. Supposing it’s a very cold night, the chill is eliminated within 10 minutes of the heating kicking in at 7am and the house is cozy within 15-20 minutes.

If you think about it rationally, For energy to be expended economically it is done so irregular in response to varying conditions/forces. When you work out, energy levels peak and trough. When you drive a car, your foot isn’t constantly on the accelerator regardless of gradient.

If you want to go through winter without your property dropping below a temp you deem cozy then by all means have the heating run 6am till 10pm every day. You’re paying a premium for it though.

What is the flow temp of your boiler to achieve comfort temp within a 15 minutes?

Also what is a comfortable temperature to you?

Analyst

What it really comes down to is, is there actually any money I could save, and if so how much. If you have a well insulated home and a very efficient heating system, it is not even worth thinking about turning the heating off. A low temperature system takes hours to reheat the house, which is another factor that makes offering universal advice to turn heating off, irresponsible.

kmcottrell

Needs to reflect wether having solar panels and underfloor heating impacts on each answer as they are increasingly being used.

Rupert1

I have replaced the main house thermostat with the programmable type e.g. from Salus. They generally cost from £20 to £40. With these you can set the temperature profile throughout the day e.g. a boost in the morning, coolish in the day when you are active and higher in the evening, low overnight. The profile can be different during the week from the weekend.

Try getting the type with a holiday feature, which acts as a frost protector while you are away and switches on the day you are coming back.