Central Heating (Hot Water) question

[TitoFan]

I had a new bolier fitted yesterday and the plumber told me that it makes no difference if I leave the hot water setting on the programming unit to 'On' all the time and there is no point in using the timer. He said that having it set to 'On' will not be using energy, unless we are using hot water, i.e the system stops heating when the water gets to a certain level and temperature and will only kick in (even if 'On') if water is used. If we are out during the day and not using hot water, leaving it 'On' will not be doing anything or using energy.

Is this true and if so, what's the point of having a timer anyway

If you're in the house, the thermostat maintains the temperature and there's no need to shut the unit off. If you shut if off, the water will eventually cool and it will take more energy to heat it back to where you want it. But if you're out for the weekend or on vacation, it makes sense to shut if off, because if not the unit will be maintaining a temperature that is not going to be needed for several days.

[Saddo]

I leave mine on all the time... no idea if its cheaper or not as I have always done this because I hate being cold and never let the house drop below 21 during the day and 18 at night all year round but the wife always maintained it is false economy turning it off and on all the time for the heating up from cold reason.

[Master]

I leave mine on all the time... no idea if its cheaper or not as I have always done this because I hate being cold and never let the house drop below 21 during the day and 18 at night all year round but the wife always maintained it is false economy turning it off and on all the time for the heating up from cold reason.

You must be incredibly rich to have it on all year round. I put it on 7am to 8.30am and back on 3.30 to 9pm and that is all for about 6 months of the year and my gas bill is about £800 per year.