Quote:
Originally Posted by jmen24
You are correct, it takes less energy to maintain the heat than to bring it back every week.
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I disagree. I think it's less $$ and less energy to turn the heater off and then reheat each weekend. Here's why. The rate of heat loss from anything is proportional to the temperature difference. To maintain 140 F water when it's, say 50F out, will take a certain amount of Btu/day, that amount can be very low with a well insulated tank or perhaps "high" with a not so well insulated tank. But if you maintain water at 140 F and it's 50 F out, it's a constant loss and thus a constant heat input needed. If you shut off the heat input, the water drops to 130 F and looses heat slower than it would have at 140 F. As more heat goes out the temp drops even more and the loss rate slows even more. Maybe your tank reaches ambient temperature or maybe it doesn't, but the heat loss per unit of time is less then it would be at the higher, maintained temperature. If your tank reaches ambient then the amount of heat/energy needed to maintain that "high" temperature would have exceeded that needed to reheat back to that "high" temperature. It's no different in concept that trying to keep a leaky bucket full.
The question is whether you really want to turn the heater off. Sure it saves energy and thus $$s; we turn ours down to "vacation temp" when we're not up. But I read last year that the various Health Depts don't recommend this. They recommend that standing water be maintained at no less than 140 F (I think that was the #) to prevent the possibility of Legionnaires disease. Now we've never had an issue in all the years we've being doing this nor have I heard of anyone I know coming down with Legionnaires so maybe it's one in a million chance, I don't know, but it's food for thought.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/
http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html