Central Heating

[Bellringer]

Is it more economical to leave the CH on, albeit low. Or, to let the house cool down during the day and at night and then have to warm it up again.

[kwicky]

Personally I would say it is analagous to either leaving your car engine running all day or starting from cold each time and we all know what the answer would be.

[missieb]

I have been advised by my boiler man that this depends on whether you have a gas or oil boiler. If you have an oil (combi) boiler it takes a lot of oil to get it up to heat so you don't want to do this just to raise the temperature a couple of degrees. So with oil it is best to have short bursts of high heat.
With gas this doesn't usually apply so it is fine to keep the house at a constant warm setting.

[matchmade]

The rate of heat loss from one object (e.g. a house) to another (e.g. the environment) is proportionate to the difference in temperature, squared. Obviously insulation delays the rate of loss, but if you keep a house at an elevated temperature all day, you are bound to lose more heat - and hence spend money to replace it - than if you switch off the heating and let the house cool down to nearer the outside temperature for most of the day.

The only thing that would invalidate this argument is if your boiler is much more inefficient from a cold start, so inefficient that it outwieghs all the energy lost if you keep it running all day.