[Greenbuilding] Nyle Geyser HPWH - Preliminary Results (was HEAT PUMP WATER HEATER)

[Paul Eldridge]

With a conventional electric water heater, every kWh of water heating 
demand represents a kWh of electricity demand, so the ratio is one to 
one; no surprise there.  Our home's space heating requirements are met 
by two high efficiency ductless heat pumps, both with a seasonal COP of 
2.7, so the heat that we sacrifice to our Nyle HPWH will have been 
provided to us at one-half to one-third the cost of fuel oil or electric 
resistance.

Let's say, for argument sake, that our DHW demands are 10.0 kWh a day 
and that our Nyle HPWH has a COP of 2.3.  The Nyle itself will consume 
4.35 kWh, so the balance that is stolen from our conditioned space is 
5.65 kWh.  Our ductless heat pumps will theoretically use 2.09 kWh to 
replace the 5.65 kWh taken away, and so if we add the two together, the 
combined total is 6.44 kWh.  Thus, even during the winter months, the 
net operating costs of our Nyle HPWH are roughly one-third less than 
that of a standard electric water heater and it will continue to do 
double duty as a dehumidifier (our dehumidifier at 550-watts is one of 
our home's major power guzzlers and anything that we can do to minimize 
its usage is a good thing).

If you heat your home with wood, natural gas or a heat pump, or if your 
passive solar gains typically exceed your space heating requirements 
then, presumably, you're well ahead of the curve; even for those with 
electric heat, it's basically a wash..

Cheers,
Paul


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Please keep in mind that an ASHPWH WILL raise the heat load and the annual
heating demand of homes in heating climates if placed with in the thermal
envelope. The amount of the increase will be proportionate to the tightness
and U value of the envelope. The tighter the house and the less conductive
the assembly, the greater the increase in heating demand will be. The
by-product of hot water is cold air.

c

*Christian Corson*
*EcoCor Design/Build*
ecocor.us
chris at ecocor.us
207 930-5088