If I have my boiler on for my central heating....

[LivingOnAnIsland]

does it use more gas if I also have my heating on? I'm trying to work out the most economical way to wash!

Aagghh sorry, that doesn't make sense - should say, if I also have hot water on. So if I have the heating on anyway does it use more gas to heat up water at the same time?

Yes, because it will have to heat less hot water if you don’t use any hot water.

My hot water is only on for 1 hour per day but the heating is on for longer than that. Although the thermostat is very low so the heaters aren't coming on at the moment.

We have electric showers so washing ourselves uses electricity rather than the water in the hot water cylinder.