HPWH (in garage) in series with Electric Water Heater (in house)?
I’m hoping to get a sanity check before proceeding with my water heater plan for a house I’m building, located in central Oregon (zone 5).
My plan is to install:
1) 50-gal Heat Pump Water Heater (GE 50-gallon model) in unconditioned garage space
> connected in series to downstream >
2) 50-gal Electric Water Heater (50-gal super insulated Marathon unit) in conditioned space in adjacent laundry room.
Some reasons this seems to be a good setup in my particular situation:
– The garage walls are CMU with 3″ polystyrene insulation board and the house is tightly sealed, so I’m not worried about heat loss trade-off due to the cooling effect in the garage.
– The house is designed for a lot of passive solar gain, and the HPWP would sit in front of a large 84″ x 60″ high-SHGC (~0.70) south-facing window in the garage, so it will benefit from solar gain.
My thinking is that this arrangement would mean that the electric water heater will almost never turn on unless I exceed 100 gallons of use, since the 50 it has been keeping warm will be the first used, and then next 50 it gets from the HPWH located two feet away in the garage will already be hot.
So… am I missing anything here?
Many thanks for any guidance!
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