Basically, is it cheaper to run a combi boiler (gas) on low setting over winter 24/7 or is it more economical to have it come on twice a day, morning and night.
Probably 2.5 hrs a morning
and 7-8 hours at night?
............. if the house is cold and you give it full blast heat for those few hours i would guess that you would be spending more in the long run
because the house will be constantly heating up then cooling down, meaning you have to have it turned up higher for longer to keep the same temp as a boiler set on low constantly.
(Does that make sense?)
I always leave mine on low setting as this keeps the house at 21 degrees which is fine for me. )
A house fully warmed up to the required temperature is like a bucket full of water with a hole in the bottom.
They both leak heat (water) at a rate that increases with temperature (water level). The higher the temperature (water level), the faster does the heat (water) pour out through the walls (hole).