I live in Phoenix, where there are times my WH is warmer than the temp
setting (it's in my non-AC garage). I do however, have a timer.. Turn it
on about an hour before I wake, and off a few hours later (for weekends).

Basically, I guess what I'm saying, is why NOT run the heater only when
needed? Even if it's only a few extra cents, it adds up - and if enough did
it, it would keep the power companies from building new plants!

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


"Phil Sherrod" wrote in message
...

On 29-Mar-2004, Edward Cheung wrote:

Nice work on the investigation. My minor comment is that you used a
standard line voltage in your
calculations. How important is this? Probably not much. In my case, I
just checked the voltage change
over one day. It peaked at 123.4V, and the min was 118.6V. If one
assumed 120V, there would be
only about 2% error

The line voltage will make no difference in the total energy usage, it
just
changes the duty cycle.

The water temperature is set by the thermostat. When the temperature
drops
below the setpoint, the thermostat turns on the heating element which runs
until the temperature reaches the thermostat's setpoint. If the voltage
is
below the standard, less heat will be generated per minute of operating
time,
so it will take longer to heat the water and the heater will run longer --
but
it will draw less power while it is running. So as long as you have
enough
voltage to generate sufficient heat to balance the energy loss (70 watts
in my
case) the same net energy will be used.

What it boils down to (no pun intended) is the law of conservation of
energy:
to maintain an average temperature in the water heater, the heat going in
has
to equal the heat being lost. The duty cycle changes, but the total
energy
used does not.