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Phil Sherrod
 
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Default Power cost of idle electric water heater


On 30-Mar-2004, wrote:

If your utility charges less at night, then you can see financial benefits
from such a timer. I believe more and more utilities will be going thois
route as they deploy more smart digital meters.


Most people have their timer set to turn their heaters OFF at night and back on
in the morning when they are ready to shower. Most of the energy consumption
will come during the morning reheat and during the period after their show when
the water heater is heating the cold water that was drawn in. So I don't see
how lower night power rates will apply.

If you are actually using water (e.g. it's flowing and regular gets heated)
then pre-heating the water by some other means (like discard heat from the
air conditioner in summer, or solar heating, etc) before it enters the tank
could save some money. Rather than merely changing the heat source, this is
more of a diversity. For example it works in winter when the A/C is not in
use, and in cloudy weather when the solar won't do so well, by drawing more
electricity only at those times, but you still get hot water at the desired
temperature.


Yes, I agree with that. Using a secondary source is definitely a good idea.
Waste heat from air conditioning is a good candidate.

A larger tank should help, given a smaller surface to lose heat from.


The closer the tank shape is to spherical, the better it is. You want to
minimize surface area for a given volume of water. However, you don't really
have a lot of choice here; I've never seen a spherical water heater.

I once was favoring tankless instant heat. But now I'm looking at that as
only a backup, if at all.


I don't think a tankless heater makes sense from an energy point of view. The
only advantage is that you have an unlimited quantity of hot water.