Heat Pump Water Heater
I’m planning a complete renovation and a second floor addition for my electric only house. The house is located in Westwood, MA, I believe it is zone 5. Currently the house is on a single 50 gallon electric water heater. We are family of 6, 4 adult and 2 kids, so I want to go with a minimum of 80 gallon heat pump water heater. Here’s the question, since the 50 gallon version qualify for $600 in rebate and the 80 gallon only have $150 in rebate, I was thinking to go with 2 50 gallon instead of a single 80. With 2 50s it will cost less in equipment and more hot water capacity then a single 80. Can 2 of the HP water heater install in the same mechanical room in the basement? Or should I separate them and put one in the attached garage. If I put them in the basement mechanical room, should I insulate the room or not? Thanks in advance.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Check the install manual for the water heater, they typically spec the space needed (~100sqft). If it is an open basement, there is no problem with more than one unit.
A cheaper solution in your case might be to hook a 50 gal heat pump in series before the existing electric tank. Set the thermostat on the resistance unit a bit bellow the heat pump. This way for typical draws, where the heat pump can keep up, all your hot water will be produced by the HPWH, if it can't keep up the resistance unit will kick in.
With a bit of creative plumbing, you can hook the resistance unit up in a thermosyphon configuration and have the HPWH handle the standby losses for both units. This might be a bit too much work to be worth the energy savings, but fun to think about.
I did a house the way Akos describes, heat pump water heater feeding conventional water heater. The conventional only kicks in if the HPWH can't keep up with the load. So far no complaints.
Sounds like a great idea. Will explore that option.