Gas central heating on constant or timer?

Wywth

neilrlsmith wrote: »

This thread is very old so really hope this comment gets picked up!

It will now you've bumped it :cool:

I suggest you try this much more recent thread for your answer
http://forums.moneysavingexpert.com/showthread.php?t=4327195

terry2

Cardew wrote: »

It doesn't matter if your house has the insulation properties of scout tent, or is built to the highest possible insulation standard, keeping heating on 24/7 at xC will be more expensive than having it timed with the thermostat still set to xC!

This is true, but the extra cost for 24hr isn't as much as many people believe.

Cardew wrote:

These threads always seem to gravitate to 'I find it better/cheaper/warmer to have the heating on 24/7 at a lower temperature than xC, rather than timed at xC'

That is because that statement is also true. However you've missed off the important bit, which is that people find themselves more comfortable in the lower temperature 24hr (and cheaper) case.

Cardew

The difference in cost between timed and 24/7 depends on the lifestyle of the occupants. If you are out at work(and the house unoccupied) for, say 10 hours a day - and in bed for 8 hours - timed will be massively cheaper.

I don't agree with your 'important bit' that people find themselves more comfortable in a lower temperature 24/7. In fact I cannot see any justification for that statement. If, say, 18C is not warm enough for me, it is not warm enough for 2 hours or 24 hours.

victor2

Cardew wrote: »

I don't agree with your 'important bit' that people find themselves more comfortable in a lower temperature 24/7. In fact I cannot see any justification for that statement. If, say, 18C is not warm enough for me, it is not warm enough for 2 hours or 24 hours.

I think the reason people can find it more agreeable to have a constant lower temperature, instead of just a higher temperature for shorter periods, is that it is the change in temperature we find harder to accept.
It is almost inevitable with timed heating that it will be set so that the occupant has periods of cooling down or not yet reached the desired level.

Timed heating at, say, 20C will always be cheaper than 24/7 at the same temperature. But 24/7 at 18C versus timed at 20C could be seen as costing less and at least as comfortable.

terry2

Cardew wrote: »

The difference in cost between timed and 24/7 depends on the lifestyle of the occupants. If you are out at work(and the house unoccupied) for, say 10 hours a day - and in bed for 8 hours - timed will be massively cheaper.

Nope! I've taken the trouble to measure it, and it is only 10% more. I'm not prepared to accept an assertion from someone who hasn't bothered to make the measurements.

I'm afraid you are missing the point (or possibly the elephant in the room), a lot of the energy in a timed situation goes into heating up the large mass that is the walls etc of the building.

I don't agree with your 'important bit' that people find themselves more comfortable in a lower temperature 24/7. In fact I cannot see any justification for that statement. If, say, 18C is not warm enough for me, it is not warm enough for 2 hours or 24 hours.

You can tweak your temperature to anything you find acceptable.

However you WILL feel more comfortable if the internal (ie within insulation) walls are at or close to the air/room temperature, rather than being 10C or more colder than the air temperature. It takes the internal walls a lot longer to fully heat up than the 6 hours you seem to believe. Once the internal walls have warmed up (mine took 48hrs for the temperature to stabilise) then you too will probably find that you can drop the thermostat setting and still feel comfortable

Cardew

terry2 wrote: »

Nope! I've taken the trouble to measure it, and it is only 10% more. I'm not prepared to accept an assertion from someone who hasn't bothered to make the measurements.

I'm afraid you are missing the point (or possibly the elephant in the room), a lot of the energy in a timed situation goes into heating up the large mass that is the walls etc of the building.



You can tweak your temperature to anything you find acceptable.

However you WILL feel more comfortable if the internal (ie within insulation) walls are at or close to the air/room temperature, rather than being 10C or more colder than the air temperature. It takes the internal walls a lot longer to fully heat up than the 6 hours you seem to believe. Once the internal walls have warmed up (mine took 48hrs for the temperature to stabilise) then you too will probably find that you can drop the thermostat setting and still feel comfortable

Firstly, the purpose of posting is not for you to accept anything, but to present an alternative opinion for other readers.

Secondly, you appear to make the assumption that your measurements(in your property) showing 24 hours heating at xC is just 10% more expensive than 6hours heating at xC , applies to all properties. The insulation standards of the property are a huge factor.

Thirdly, far from me not appreciating the situation, it is the very fact that the fabric of a house is a huge ‘thermal store’ that makes any comparisons of cost difficult. The only way to make a comparison is to measure the 24/7 costs over a period of several days, then let the house ‘cool’ down for several days and repeat the measurements with heating on 6 hours a day.

Of course this experiment must be repeated over several days with exactly the same weather conditions, same consumption of hot water etc etc.

terry2

Cardew wrote: »

You appear to make the assumption that your measurements(in your property) showing 24 hours heating at xC is just 10% more expensive than 6hours heating at xC , applies to all properties. The insulation standards of the property are a huge factor.

Well strictly speaking, in the 24hr case, we are in a steady state situation, and so the only thing at play is the heat loss from the building, so the insulation is the only factor.

And no, I am not making the assumption that it applies to all properties, I am merely reporting on my property. I have said elsewhere that people need to make their own measurements. However, given my rather odd house layout and some suspected dodgy insulation in areas that are too expensive to rectify, I suspect that my case is worse than the norm, and that in many cases other people would use less heat than the extra 10% I measured.

Far from me not appreciating the situation, it is the very fact that the fabric of a house is a huge ‘thermal store’ that makes any comparisons of cost difficult. The only way to make a comparison is to measure the 24/7 costs over a period of several days, then let the house ‘cool’ down for several days and repeat the measurements with heating on 6 hours a day.

I apologise if I have misremembered who said what. Note you don't need the several days of cool down in between, just switch to the new state but remember to allow it to stabilise before taking measurements.

Of course this experiment must be repeated over several days with exactly the same weather conditions, same consumption of hot water etc etc.

The hot water usage is a only a small effect if you are measuring during winter. You don't have to have identical conditions, just include external temperatures and make more measurements. I spent many months measuring daily gas usage and plotting that against minimum external temperatures, and got a series of graphs for the different test conditions I was trying. So I know just how much cheaper my current comfortable state (thermostat at 17.5C 24hrs) is compared with the supposedly cheaper 8hrs a day thermostat at 20C (values that were needed to make the house feel comfortable). Note that the state 'thermostat at 19C 24hrs' for my house had the same gas usage as 8hrs a day thermostat at 20C.

But I agree every house is different and people need to make their own measurements. They should not be discouraged from doing that.

closed

how many kwh of gas have you used in the last 365 days to maintain your house at 17.5 degrees C 24/7? What it the type and size of dwelling, how many radiators/rooms?

From your graphs during the 24/7 test what was the maximum kwh (gas/heating) usage in any one day, and what was the average outside temperature during that day

Cardew

closed wrote: »

how many kwh of gas have you used in the last 365 days to maintain your house at 17.5 degrees C 24/7? What it the type and size of dwelling, how many radiators/rooms?

From your graphs during the 24/7 test what was the maximum kwh (gas/heating) usage in any one day, and what was the average outside temperature during that day

Not forgetting the TRV settings on each of the radiators;)

terry2

closed wrote: »

how many kwh of gas have you used in the last 365 days to maintain your house at 17.5 degrees C 24/7? What it the type and size of dwelling, how many radiators/rooms?

in the 12 months up to 28/2/13 I have used 30598 Kwh of gas (previous 12 months was 24369 Kwh, - note boiler was replaced in 2010 so earlier values won't match).
Property is a bungalow that has had both a loft conversion and a ground floor flat rooofed extension (extensions done by prior owners) - there is a lounge, dining room, kitchen, 6 bedrooms, two bathrooms and one shower room, most rooms have one radiator but the lounge has two.,

From your graphs during the 24/7 test what was the maximum kwh (gas/heating) usage in any one day, and what was the average outside temperature during that day

The measurements were all done some six years ago, and I will need to dig-up the notes to find the individual daily results (though I vaguely recall peak usage as being bout 6.5 gas units with minimum outside temps around -3C, for both the 24hr and timed states (but remember that was with an older boiler)). Note that I was mainly interested in the minimum temperature over a 24hr period, as that is when the heat loss would be the greatest (although I think I also noted the maximum too, but that wouldn't help to give a meaningful average).