Phil Sherrod wrote:
On 29-Mar-2004, Bill Vajk wrote:

Your numbers are nice and thanks for posting the info,
however it seems to me 114 is a little on the low end,
with 120-125 being more common and I run my domestic
hot water at 140F.

Since the energy loss is directly proportional to the temperature differential
of the stored water and the air temperature around the tank, it's easy to
calculate how much more it would cost to maintain the water at 140F.

Assuming a room temperature of 61 degrees F around the water heater:

Cost to maintain water at 114F with 8 cents/KWH cost = $4.00/month (53 degree
differential)

Cost to maintain water at 140F with 8 cents/KWH cost = $5.96/month (79 degree
differential)

Ideally, yes. I do wonder, however, what the startup cost of
the electric heating element(s) is. A higher cycling rate
isn't going to present a linear extension based on delta T
alone since the current consumed during the period the
heating element takes while coming up to operating temperature
is higher than at near steady state operation.

The water temperature, as it rises, results in successively
higher operating temperature of the heating element with a
corresponding (albeit small) decrease in the current drawn.
I don't know what the typical slop in the thermostat
temperature is for an electric hot water heater.

Yes, I realize I'm nitpicking, but that's part of the fun
in discussions like this one. :-)

Your numbers are plenty close enough for the average guy.