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This type of water heater uses a compressed gas to produce heat,
instead of a resistive electrical heating element. They can save over 60%
of the energy consumed by a standard electric water heater. This works out
to a savings of $320 a year on average. The cost is about double that of a
standard water heater, with a payback on average of 3-5 years. With an
expected lifespan of 13 years, it could save you around $3000 over its
service life.
There are some issues with noise and installation location
issues, so do your research before you buy one.
 It's
generally easier to move something than to make something. Putting that
principle to use, heat pump water heater (HPWH) technology uses
electricity to move heat from one place to another instead of generating
heat directly.
To understand the concept of heat pumps, imagine a refrigerator
working in reverse. While a refrigerator removes heat from an enclosed
box and expels that heat to the surrounding air, a HPWH takes the heat
from surrounding air and transfers it to water in an enclosed tank.
A low-pressure liquid refrigerant is vaporized in the heat pump's
evaporator and passed into the compressor. As the pressure of the
refrigerant increases, so does its temperature. The heated refrigerant
runs through a condenser coil within the storage tank, transferring heat
to the water stored there. As the refrigerant delivers its heat to the
water, it cools and condenses, and then passes through an expansion
valve where the pressure is reduced and the cycle starts over.
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Water heating energy usage comparisons
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Water Heater Type
|
Efficiency
|
Installed Cost
|
Yearly Energy
|
Life
|
Total Cost
|
|
Conventional gas storage
|
0.60
|
$850
|
$350
|
13
|
$5,394
|
|
High-efficiency gas storage
|
0.65
|
$1,025
|
$323
|
13
|
$5,220
|
|
Condensing gas storage
|
0.86
|
$2,000
|
$244
|
13
|
$5,170
|
|
Conventional oil-fired storage
|
0.55
|
$1,400
|
$654
|
8
|
$11,299
|
|
Minimum Efficiency electric storage
|
0.90
|
$750
|
$463
|
13
|
$6,769
|
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High-eff. electric storage
|
0.95
|
$820
|
$439
|
13
|
$6,528
|
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Demand gas (no pilot) 5
|
0.82
|
$1,600
|
$256
|
13
|
$4,925
|
|
Electric heat pump water heater
|
2.20
|
$1,660
|
$190
|
13
|
$4,125
|
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Solar with electric back-up
|
1.20
|
$4,800
|
$175
|
13
|
$7,072
|
Sources:
American Council for an Energy-Efficient Economy
U.S. Environmental Protection Agency and the U.S. Department of Energy
General
Electric
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0 comments • JJ and Suzanne Greive - Seattle Area ASHI Inspections • January 19 2011 01:27PM