radiators always on vs switch on when needed

b56c

What is the most efficient/cost effective method for heating a house with gas-fuelled radiators for the average house and household? Leave them on all the time, at a lower thermostatic setting, increasing the setting when you're home or begin to feel chilly OR only switch on when you feel the need or for timed periods throughout the day. So basically what I'm asking is: is it cheaper to heat from cold or to keep on all day/night at reduced setting?

TheBees

Good question. I've often wondered this too. My Dad reckons its best to leave on most of the day at a low setting instead of it having to warm up from cold but if we are out at work and school it seems a waste.

Thirtyniner

I asked my service engineer that very question as I've always been sceptical about the always-on theory. He said it all depends on the insulation and draughtproofing efficiency of the property. If the heat loss is minimal, always-on works; if it's old, exposed and draughty like mine, on/off twice a day and warm clothing is more economical. Sounds logical to me. I'm in the process of increasing my insulation right now.

foreign_correspondent

My radiators do not seem to have any heat setting adjustment - they are either on or off, at full belt. I can set the timer, but not the temperature.

mech_2

If the question is "Which is better: constant or timed?", then the answer is always timed, no matter how much insulation you have. Added insulation is likely to make the same percentage saving with either heating regime, as the house is unlikely to cool down entirely on a daily basis between the times set on a timer, so heatloss carries on all day and all night.

On the other hand, if the question is "Which is better: timed or constant on lower room thermostat settings?" then the answer is "It depends". It depends how much lower "lower" is. And it also depends whether you genuinely can get away with significantly lower temperatures when the house is heated constantly. I'm inclined to believe that it does help (having tried various combinations), but it's far too subjective a question to put a figure on it. But if it's a load of hogwash, then the answer could quite possibly be: "It's a trick question. Low and timed is best".

It's probably worth putting the savings into context. I tried measuring gas consumption on timed versus constant using the same thermostat setting last winter and plotted this against outside temperatures. It's a 3-bedroom semi, one occupant, with incomplete insulation and a condensing combi boiler. I saw an increase in gas usage of just under 13% when on constant compared to timed for 1.5 hours in the morning and 6.5 hours in the evening. The increase in the bill will be less than this because of standing charge/higher 'tier 1' rates.

Turning the thermostat down 1 degree saves around 10%, so you can see how little is needed to tip the balance. 1.5 degrees lower on the thermostat and constant heating could win, at least in my case.

Service engineers are more likely to favour "low and constant" option if you have a condensing boiler (practically all gas boilers installed in the last 3 years), because then you can set the water temperature very low and this is likely to be kinder to the boiler's heat exchanger and extend its life. The house will still get to the set temperature, but much more slowly, so heating the house constantly becomes the more practical option. This piece of reasoning doesn't need to assume the running costs will be lower though.

Cardew

Mech is absolutely correct in his reply.

This question is asked hundreds of times and there is no answer to 'High in Bursts' or 'constant at low'

It is like asking will I get to my destination quicker if I drive at 120mph for some of the time and then pull into a layby for a rest, or drive constantly at a steady speed.

It depends of how long you drive for at 120mph and what is your steady speed.

I think most of the questions about heating are because of the belief that it takes more heat to warm up a house from cold every time, than keeping it at a constant temperature; and that is an 'Urban Myth' with absolutely no truth to the statement at all.

mell242

I've been wondering about this too. We live in a detached bungalow with gas central heating but no thermostat so we can only change the temperature generated by the heaters via each individual heater. We do have a timer so can set the heating to come on at a particular time.
Since it's got colder I tend to do short bursts of heat rather than leave the heating on constantly. I've no idea if it's costing us lots more money though!

Thirtyniner

Mech and Cardew seem to have it taped: depends on many factors, some of which I suppose are how many people in the house going in and out, and how good we are at keeping internal doors closed.

Could it be that Foreign Correspondent's system may have had a room stat which a previous owner did away with. My mother always used to operate her system via the on-off switch with the room stat on high.

If Mell242 is describibg Thermoststic Radiator Valves, my system has those instead of a room thermostat. Works fine although some of them stick open and I have to free them up each Autumn. I also blow out any fluff in the heads, and I have a bottle brush taped onto a piece of cane to clean out the middle of the double radiators; dusty work but worth doing.