On 29-Mar-2004, "AZ Woody" wrote:

I live in Phoenix, where there are times my WH is warmer than the temp
setting (it's in my non-AC garage).

Wow, your garage is 120+ degrees? Do you cook roasts out there too?

In that case, your heat loss from the idle water heater would be $0.00

I do however, have a timer.. Turn it
on about an hour before I wake, and off a few hours later (for weekends).

There's nothing wrong with that, but your savings are probably miniscule. When
you turn the heater on, it is going to run long enough to heat the water to
whatever temperature the thermostat is set for; that might take 15 minutes of
continuous running. The measurements for my water heater show that the total
on-time for the heating element is 23 minutes per day (accomplished by only a
few cycles per day).

Let's say the average temperature in your garage is 85 degrees (vs. 61 in my
crawl space) and your water temperature is the same as mine -- 114 degrees.
You've got a temperature differential of 29 degrees, and I've got a
differential of 53 degrees. Then your cost of heat loss (assuming 8 cents/KWH)
is about $3.28 per month. I would be surprised if your timer dropped the
average water temperature enough to halve the heat loss, so you may be saving
$1.50/month if you're lucky.

Do you turn off the lights if a room is empty? Same thing.

No it's not the same thing. When you turn on your water heater, it runs until
it heats the water to the set temperature; the longer it was off, the longer it
has to run to make up for the temperature drop. Unless it's off for a long
time, the energy required to restore the temperature will come close to
matching the energy that would have been required to hold the temperature
constant. On the other hand, when you turn on a light, it doesn't have to
make up for the darkness that existed while it was off.