Some HPWH Room Air Temp Data

fentonc

The cooling effect on the surrounding room when running a heat pump water heater is something that gets discussed a lot with relatively little concrete data involved. I have a 50 gallon Bradford White Aerotherm providing DHW for our 3 person household. The water heater is located in a small mechanical area (next to the boiler) off of a ~400 ft^2 workshop and connected via an open door to another ~400 ft^2 play room / storage area. The room air temperature sensor is located in the play room right next to the connecting door.


Only the first floor heating zone is enabled at the moment, so the basement is unheated except for any residual heat given off from the boiler (with the boiler averaging about 1.6 therms/day during the period shown). The HPWH running seems to be associated with a temporary 0.2F drop in the air temp and a temporary ~1% drop in relative humidity. The biggest takeaway is just that it's a very, very small effect overall. So far it's probably been averaging about 2 kwh/day consumption (estimated, not actually measured), vs ~0.6 therms/day for the gas water heater it replaced.

I'm looking forward to collecting some data in the middle of the winter to see if it actually impacts overall gas consumption when the boiler is actively maintaining the temp in the basement.