On Thu, 07 Aug 2008 09:46:19 -0700, Smitty Two
wrote:

SNIP

This problem is a minor modification of the jacuzzi heating question,
and the same logic applies. Every speck of heat lost through the night
has to be replaced. Do it in small chunks, or do it all at once. Same
amount of energy is expended, disregarding the *very* minor difference
noted (that rate of heat loss decreases as temp. differential decreases.)

I believe you are on the right track. I have nothing to back up my
theory but here goes. It seems to me you only save after the tank
water temp has cooled to incoming water temp. Then the time off would
be the same as never having turned it on. This, assuming you have done
the other things such as insulation and stopping leaks.

--Andy Asberry--
------Texas-----