I have my gas boiler on a timer (comes on in the morning) and usually put it on for a few hours in the evening. I assume this is the most cost effective way of heating the water. The other school of thought is to leave it permanently on 24/7 as apparently it takes more energy to heat the water from cold than to keep it warm. Anyone have any ideas as to which method is most effective for energy conservation/money saving? Have looked about but there doesn't seem to be a definitive answer.