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Looking for Hot Water Heater Efficiency comparison

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Posted by Epictitus on April 8, 2007, 4:35 pm
I was in the Borg yesterday looking at electric hot water heaters.

None of the products had EnergyStar or EnerGuide ratings.  The sales guy
told me that it doesn't really matter and they're all the same anyways.
Shame on GE and HomeDepot.

Does anybody know of a link that allows me to compare the energy efficiency
ratings of electric water heaters?

I can't find ANY product comparisons, only articles telling me what to look
for and compare.

Sites that don't have useful info on specific products:

I can get lists of refrigerators, dishwashers etc. but NOTHING comparing hot
water tanks.

Anybody have any experience using the on-demand or tankless systems?  Do
they really save money?

Gas is not an option for me but solar may be - except that I'm in a colder

Posted by beemerwacker on April 8, 2007, 4:15 pm


Hey Mike,

Our heater took a crapper a few months ago and I looked into the
tankless deal. The initial outlay for the tankless system is pretty
high. You need a larger gas line into the house and they're more
expensive so I just spent the grand on a regular energy efficient
unit. Blinking lights and crap all over it. Like a stinking rocket
ship in the basement.


Posted by CJT on April 8, 2007, 7:35 pm
 Epictitus wrote:

All electric hot water heaters (and electric heaters in general) are
100% efficient by definition.  Think about it.  All the energy consumed
is turned to heat.

The e-mail address in our reply-to line is reversed in an attempt to
minimize spam.  Our true address is of the form che...@prodigy.net.

Posted by BobG on April 8, 2007, 8:06 pm
 The only ineffciency in the hot water heater is heat flow through the
walls, and having to push a gallon of cold water out of the pipe in
front of the hot water. If you get the tank heated up and dont use any
hot water, it probably wont need to com on for hours, and then only
for a few minutes. Put a neon light across the heater and see if it
comes on after you wash your hands or do some minor hot water use.
Seems like the main selling point of these instant on hot water
heaters is 'you never run out of hot water'. I bet if you run out of
hot water with a 40 gal tank with 2500 watt elements, you wont run out
with a 50 gal tank with 4500 watt elements.
I bet cost per gallon is exactly the same for two systems with same
temp setting and intake water temp.

Posted by nicksanspam on April 8, 2007, 8:10 pm

DOE says:

 The Energy Factor (EF) is the measure of the overall efficiency for a
 variety of appliances.  For water heaters, the EF is based on three
 factors:  1) the recovery efficiency-how efficiently the heat from
 the energy source is transferred to the water; 2) standby losses-
 the percentage of heat lost per hour from the stored water compared to
 the heat content of the water; and 3) cycling losses.

For an electric storage water heater, this boils down to standby losses.
 The EF is determined under specific test conditions; for reference see:

 Here are the current minimum energy efficiency standards for water heaters
 manufactured on and after 01/20/2004:

 Product Class.....Energy Factor

 1. Gas fired....0.67 - (0.0019 X rated storage volume*)
 2. Oil fired....0.59 - (0.0019 X rated storage volume*)
 3. Electric.....0.97 - (0.00132 X rated storage volume*)
 4. Tabletop.....0.93 - (0.00132 X rated storage volume*)
 5. Instantaneous Gas-fired....0.62 - (0.0019 X rated storage volume*)
 6. Instantaneous Electric.....0.93 - (0.00132 X rated storage volume*)

 * Rated storage volume = the water storage capacity of a water heater,
 in gallons, as specified by the manufacturer

Here's an example:



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