On Aug 7, 9:49*am, Smitty Two wrote:
In article ,





*"PanHandler" wrote:
"Smitty Two" wrote in message
news

I don't think it'll save you a plug nickel. The amount of heat lost
during those 10 hours is exactly the amount of heat that has to be put
back in. It doesn't matter one whit whether it's done all at once in the
morning, or incrementally throughout the night.

There is one caveat. If your water heater is so poorly insulated or so
unfavorably situated that the water temp inside returns to supply
ambient before those ten hours elapse, then you'll save. Since you're
obviously energy conscious, that caveat likely doesn't apply.

What about me?
My WH is on for one hour daily (manually, when I get up in the AM). I take
my shower and wash dishes, then shut it off . There's still enough residual
hot water during the day for hand washing, etc. My clothes washer is only
used with cold water.

I doubt you're saving anything. If you used hot water one day per week,
then it might save you to shut it off for the other six days. For all
intents and purposes*, you don't save until it's been off long enough to
cool down to whatever temp your cold water supply is.

*Someone will no doubt offer that the greater the temperature difference
between water in the tank and the surrounding air, the faster heat will
be lost. So it's theoretically possible that my original statement ("It
doesn't matter one whit whether it's done all at once in the morning, or
incrementally throughout the night.") isn't *exactly* true, it's
probably within a few pennies of being true.- Hide quoted text -

- Show quoted text -

It's not "theoretical" that your original statement is incorrect.
From elementary physics, which you yourself cite above, it's clear
that a water heater turned off all night will use less energy than one
left at normal temp. Now, whether the savings are enough to make it
worthwhile to install a timer, is an entirely different question.

Here's what the DOE has to say:

http://www.eere.energy.gov/consumer/.../mytopic=13110

"Install a Timer and Use Off-Peak Power for Electric Water Heaters

If you have an electric water heater, you can save an additional 5%–
12% of energy by installing a timer that turns it off at night when
you don't use hot water and/or during your utility's peak demand
times."


So, if you have a bill of $20 a month, that's $12 at the low end.
Maybe not enough for some to consider, but clearly more than a plug
nickel.