[RE-wrenches] Heat pump water heater

William Korthof wkorthof at eesolar.com
Sun Apr 11 13:37:30 PDT 2010


Does anyone have experience with heat pump water heaters? 

There are a couple units available now and they seem great---I just purchased one from 
Lowes (GE "hybrid" water heater), which has a 700 watt heat pump and 2 standard 4500 
watt heating elements... the "brains" of the water heater let you select several operating 
modes: 
-heat pump only
-heat pump with limited resistive backup
-heat pump with maximum resistive backup
-resistive heating only 

The unit has a rated COP of 2.35, which should mean 2.35 kWh of heating for each 
kWh of electrical load (presumably in mode #2 or #1), and the DOE energy sticker shows 
the thing using ~1800 kWh per year, compared to standard tanks using ~5000 kWh/year. 

For the $1600 price, it seems like a no-brainer replacement for any regularly used 
electric tank heater--- and with this efficiency, I'm wondering how it might compete 
against the other hot water options: gas tank, propane, solar, tankless....  
Rather than DHW solar, it now make more sense in many cases to just have a heat pump 
water heater + a few more PV modules.... all electric, and no solar hot water maintenance. 

/wk


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