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

NowRetired

The programmer never switches the heating boiler off it actually sets the thermostat to 10C min or which ever higher temperature you specify.

So even if there is no demand for heat if the temperature is above 10C, the boiler is still switched on and using gas?

My heating switches off and uses no gas or electricity if the temperature is above what the thermostat is set at.

147718

johnsiddle wrote: »

My grand daughter has just purchased a brand new house from Taylor Wimpy.
The combi boiler fitted uses a remote, all in programmer/room stat.
The programmer never switches the heating boiler off it actually sets the thermostat to 10C min or which ever higher temperature you specify.

how does this fit in with the advice to turn the boiler off when not needed.
Is this boiler so very in-efficient?????

:T:T:T

My experience with combi boilers is that the boiler is only firing when heat is required. For instance in the summer when no room heating is needed the boiler will be dormant until the hot water tap is turned on then the boiler will fire up
I would also have thought that if the temperature has dropped to 10 C in the room you do need heat
I consider combi boilers very efficient particular for 2 people and for when folk are absent from the house during the day

hpforever

If you are able to instal a heat pump, then it is generally cheaper to run than oil or gas. We have had one for the last 5 years, along with 4 Kw of solar pv cells. I take readings of consumption and max & min temperatures every morning and should be glad to share details with anyone interested.

Hugo_Rignold

I am astonished that the EST should make such a blanket statement, and by all the 'expert' advice one way or the other.

The constant vs timed heating question hinges entirely on the nature of the building. If you have a modern house of relatively lightweight construction (like all cavity walled houses for example), it will have low thermal mass, and consequently heat up and cool down quickly. In which case it makes sense to heat it wehn you want to use it and not the rest of the time. If you have a a solid-walled farmhouse with metre thick walls it will have very high thermal mass and heat up and cool down very slowly. In which case you maintain a constant much lower level heat, effectively using the fabric of the building as a giant storage heater.
This is the same principle by which underfloor heating fed by heat pumps works, for example. It is also the reason old farmhouses tended to have an aga or rayburn ticking over 24/7 to keep the place warm. If you let a heavy solid old house get cold and then whack on the central heating half an hour before you get home then all you are doing is heating the air around the radiators: it will not have time to make any siginifcant difference to the overall temperature before you switch it back off again. Conversely, if you have a 1992 semi-detached, switching the heating on half an hour before you come home will have the place nice and toasty by the time you come in. keeping it on while you are out serves no purpose.

There is no 'one-size-fits-all' heating strategy. It always comes down to what you are trying to heat.

spinningsheep

Exactly Hugo Rignold, my friends who live in a new build apartment can put their heating on for 20 mins and the whole flat is toasty and remains that way for some time, my parents have a 1977 3 bed detatched with loft and cavity insualtion and they have their old Glowworm boiler on its lowest setting yet the house is still roasting, my 1900 4 bed end of terrace takes at least 3 hours to warm up from cold, and if you "warm her bones" so to speak, the boiler hardly needs to work at all to keep the place toasty warm.

John_Pierpoint

If you are able to instal a heat pump, then it is generally cheaper to run than oil or gas. We have had one for the last 5 years, along with 4 Kw of solar pv cells. I take readings of consumption and max & min temperatures every morning and should be glad to share details with anyone interested.

Welcome to the forum.

If you pop along to this thread we would all be interested in the performance of your PV panels.

http://forums.moneysavingexpert.com/showthread.php?t=3853851

There have been many threads in the last half a dozen years about heat pumps, while the UK's installed number has climbed tenfold.

It rather depends on what sort of house you have and what sort of heat pump - beware it is like being a member of a religion and arguing about your God versus all the others.

Almost as bad as this thread, while everyone on the PV thread knows they are farming the subsidies, and the discussion is more like how long will it be before "net billing" makes sense.

Never in the UK?

tichtich

Hugo_Rignold wrote: »

The constant vs timed heating question hinges entirely on the nature of the building.

Sorry, but it really doesn't. It's just basic physics.

Hugo_Rignold wrote: »

If you let a heavy solid old house get cold and then whack on the central heating half an hour before you get home then all you are doing is heating the air around the radiators: it will not have time to make any siginifcant difference to the overall temperature before you switch it back off again.

Sure, half an hour might not be enough. Give it as many hours to reheat as needed. Even if you have the heating off for 4 hours and then on for 4 hours (when you're out for 8 hours), you will still save some energy, however little.

As soon as you create heat it starts dissipating into the atmosphere, so you don't want to create it any earlier than it's needed. Whatever heating is needed to make the house warm when you get home, it's better to do that heating in the later part of the period that you're out, rather than in the earlier part.

The sooner you heat, the more heat you lose. So the longer you can delay the heating the better.

The nature of the building will influence the size of the saving, and the saving might be very small in some cases, but it can't possibly be negative. I.e. it can't possibly be cheaper to have the heating on all day than to switch it off for part of the day.

P.S. If the building is so massive that it takes many hours to heat up, then it will also be relatively slow to cool down, so it won't cool down by much in 4 hours.

Cardew

Originally Posted by Hugo Rignold


The constant vs timed heating question hinges entirely on the nature of the building.

tichtich wrote: »

Sorry, but it really doesn't. It's just basic physics.

100% correct - it is basic physics and the EST are absolutely correct to make such a statement. i.e. the longer the boiler is off the less heating fuel is used.

The best illustration of this was given earlier.

Take a building - any building regardless of construction - that is to be left empty for, say, two years. I cannot think of anyone who would suggest that it would be cheaper to leave the heating on 24/7 rather than switched off.

That is just basic physics, as the house cools down there is less heat transfer from the building to the outside and eventually there will be no heat transfer as the house will be at the sme temperature as outside.

So how about one year?

A month?

A week?

A day?

An hour?

At what point do the basic laws of physics not apply?

If you have a a solid-walled farmhouse with metre thick walls it will have very high thermal mass and heat up and cool down very slowly.

Correct, that is not in dispute; however what is the relevance?

With the heating off, if the farmhouse takes, say, an hour to lose 0.1C from 20C to 19.9C, at 19.9c it will be losing heat at a lower rate than if the house was maintained at 20C.

John_Pierpoint

Let me widen the discussion and the understanding a bit.

Britain is almost unique, we are unbelievable far north of the tropics, where the sunshine delivers most of the energy from the sun. For example think of a southern hemisphere town such as Hobart (dangling below Australia) and tell me where that would be in Europe.
The Gulf stream is unique, while the rest of the world has a climate, we have weather. So with cheap fossil fuels for the last 250 years it has made sense to build cheap draughty houses [I have recently sold one it cost £300 in 1870 and in 1931 it was bought for £250 – I sold it for nearly £400k]. In a cheap draughty house with cheap fuel, one only needs to heat it when needed, on a day when the weather is looking bad. As the cooking was on a coal range there would always be something burning, if only to keep out the damp fog, rising from that warm sea.

Meanwhile in the continental countries, not floating in nice warm sea, the climate tended to dictate the building of thick walled buildings, in which people huddled together in flats.
It snowed in November and melted in April. Most of these countries were not sitting on a mountain of coal and surrounded by a sea of gas – so they had to learn how to make the best of the little expensive fuel they had. [Double doors, double windows with shutters, huge free standing stoves, not open fires]

Now that we have tripled our population, burnt our natural resources of fossil fuel and now been told by our government to survive on the same carbon ration of fuel, as burnt in 1825; we need to learn a whole new method of survival.

Some people have already discovered that when a house is insulated to “Continental” standards and heated by a boiler that needs “cold” water coming back from its heating coils (preferably running at 35 degrees in the floor slab – Roman style) then the rules change. Try to heat the home too quickly and throw an extra 10 percent of the heat into the garden. Turn radiators on and off with temperatures oscillating by 3 degrees and the average temperature in the home needs to be two degrees hotter as the radiators don’t offer a constant radiant heat. [Our American cousins refer to the new strange (to them) concept of under-floor heating as “a radiant floor”]. At the sort of temperatures we are discussing the loss of heat from a building is proportional to its excess temperature.
With radiant heat bouncing back off warm walls floors ceilings and even coated glass we feel comfortable – the comfort of 15 degrees in October, no wind but with a little sun to warm your face.

The next big step will be getting used to living with a heat pump – this really is “trickle” technology that needs “heuristics” as operating a floor slab heated with half price over night electricity and topped up with day time trickle, needs an understanding owner and a clever system that knows we have “weather” in the UK and responds accordingly.

What it most definitely does not want is a human trying to drive it who has been told “turn it off when you are not at home and when you are turn it down and save lots of money”.

Cardew

John_Pierpoint wrote: »

Let me widen the discussion

The next big step will be getting used to living with a heat pump – this really is “trickle” technology that needs “heuristics” as operating a floor slab heated with half price over night electricity and topped up with day time trickle, needs an understanding owner and a clever system that knows we have “weather” in the UK and responds accordingly.

What it most definitely does not want is a human trying to drive it who has been told “turn it off when you are not at home and when you are turn it down and save lots of money”.

John,
With respect you have widened the discussion too far by bringing heat pumps into the thread.

Firstly a heat pump is not a heater.

It is an appliance to extract and transfer heat from the outside ground or air into the house.

The reason that it is not recommended to 'turn the temperature of a heat pump down when out of the house' is because they have a lowish heat output, which together with water at a relatively low temperature, means it needs to run long periods(or 24/7) to keep the house at an acceptable temperature.

Indeed one of the criticisms of heat pumps is that they have to use electricity to heat the house when there are no occupants, or the occupants are in bed.

That said heat pumps still obey the laws of physics, if you turn them off for a period you will use less electricity than keeping them on 24/7.