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

macman wrote: »

I can't imagine why MSE Guy is perpetuating this stupid myth by starting a 'debate' that has been done to death on here every time the weather turns chilly!
Might as well start a thread on whether Neil Armstrong really walked on the moon...

- I can, his job is introduced conversational controversy to keep the post count up
- maybe there's an office bonus to someone whose idea generates 1000 # per thread posts
- there I go, I'm making one more # towards his bonus, silly me

howee wrote: »

But this is money saving and tumble dryers waste a lot of money 30-50p per hour. Agree about mould (I perform property surveys), and the advice should also come with a caution (in some cases), especially "if" there has been mould or damp issues.

My tumble dryer is cheap to run and wastes precisely zero energy.

It's AAA of course, and condensing, and it's run at night on e7. It uses 1.8kWh per cycle with straight from the machine spun clothes, which costs me 10.6p. Because it's condensing and is situated in the living area, the 1,8kWh it consumes contributes to the room heating. In fact, it is much better than my storage heaters for that amount of heating, because it dries clothes as well as heating the room.

If the washing has been on the line for a while but not fully dried (typical in cold/damp weather), then it uses 1kWh to dry.

I've measured the consumptions several times now, with an accurate enough plug in monitor (much more accurate than an Owl or any other clip on device) - mainly because it is lower than I expected.

howee wrote: »

But it's not running all the time that's the reason my bills are low £56 per mth (4 bed detached 10yr old), the heating only kicks in if its needed, I was in on Sunday and the heating never kicked in. The same applies at night it does not kick in unless its bitterly cold outside. The digital stats are fantastic as the temp only has to vary by .5 degs before it cuts in which means you don't get variations in temp like you do with an old mercury switch type.

Of course if you prefer to go cold before the heating comes back "only another hour throw me a blanket" then that's fine but not for me.

I'm really struggling to believe your house looses no heat at 20c for an entire night when the outside temperature was around -1 to 2c depending on where you live.

I live in an 8 year old 5 bed and my bills are £130 a month in gas at the moment. It seems to loose 0.5c per hour or 2 at the coldest. And at 7c outside it will hold a temperature for several hours.

It seems the low point where heat drop off rapidly decreases for my house is 13.5c in the hall or around 15c downstairs and 16c upstairs. It could stick here for 24hours.

But at 20c surely it's loosing heat every hour? Meaning your boiler is constantly topping up.

I infact run my heating from 6am to 11pm regardless of the day, but no need to have it on overnight.

oldskoo1 wrote: »

I'm really struggling to believe your house looses no heat at 20c for an entire night when the outside temperature was around -1 to 2c depending on where you live.

A house that lost no heat at all would be quite something, wouldn't it? If houses retained 100% of their heat then the "keep it on all the time" argument would make sense, although we probably wouldn't need heating systems at all - the builders could just warm it through when they finished the house and that would be that.

Unfortunately, if the efficiency of the insulation is less than 100% then any time we heat a house we are losing energy into the atmosphere. So it stands to reason that the longer we heat the house above the outside ambient temperature, the more energy we lose. Modern houses with good insulation will make "always on" a more feasible option, but it's always going to cost more than not having the thermostat up all the time.

Also, the greater the difference in temperature between the house and outside, the faster the rate of cooling (as per Newton's Law of Cooling). As oldskoo1 has noted, temperature doesn't drop in a straight line until it's the same as outside - it cools quickly at first and then more slowly.

Taking it to the logical extreme, "always on" theory would suggest that it doesn't matter what temperature you had your thermostat set to, as once you reached it, it would then take next to nothing to 'top it up'. This is plainly false. If you ran a blast furnace in your cellar and kept your room temperature at 60c you would lose drastically more of that heat in an equivalent time than someone whose room was at 20c. On a much smaller scale, the same idea applies with thermostats set at 21c and 20c, although as it won't put £40,000 on your energy bill it's less likely to be noticeable.

It never ceases to amaze me how many heating engineers are adamant that "always on" is the most cost-effective way of heating a house. I can understand why a lot of people prefer doing it, and if you have a well insulated house and are sensible with the thermostat then the level of additional expense might well be worth the extra comfort, but it doesn't stack up based on the science.

david29dpo wrote: »

Lets cut the chase.

If it`s on it uses energy, if it`s off it don`t.