Good detailed analysis. The ground-source HP makes it work better (even better if the dryer and water heater are ground source too) but I can't imagine the HP dryer or water heater is great for a carbon-heated home (or my lower-COP(?) HP-heated one).mf1982 wrote: ↑ I have both a heat pump dryer and heat pump water heater. When the dryer is running, the "waste" heat is absorbed by the water heater.
In terms of the math on the water heater energy wise:
My Rheem unit has a COP of 3.8 (1kWh electricity = 3.8 kWh of heat moved)
My home is heated by a ground source heat pump at a COP of 4.0.
My effective water heating COP during the heating season is still about 2 because I need 1 kWh to bring 4 kWh of heat into the house, then another kWh to put those 4 kWh into the tank, so for every 4 kWh of heat into the tank I need to use 2 kWh of electricity.
At my rental property where I have a similar set up but the home heating is provided by cold climate air source heat pump
DHW COP 3.8
Heating COP 3.8 - 2.0 (drops below 2 at temperatures below -18°C I believe, without looking it up again)
So in that case I need to use 2 kWh of electricity to bring 4 kWh of heat into the house in the cold of winter, then 1 kWh of electricity to put those 4 kWh into the hot water, so the COP is only 1.33. When temperatures are 8°C or above it's 1 kWh ot bring the heat in, 1 kWh to put the heat in the tank, so COP of about 2 again
From mid-May until mid-September when the home is not being heated the COP of the water heater is the full 3.8. You could argue that during the cooling season (mid-June to mid-September) the COP is even greater as the cool air expelled from the unit, and the dehumidification from the unit are "free". I'd be paying for those functions separately anyways, but in this case the waste heat energy is being used for a function.
It would seem the HP dryer and water heater would be much more effective if you live in the southern/south-eastern U.S. as it serves to cool and/or dehumidify which is something pretty much required year-round.
I smile when I see container ships sailing past my house laden with stuff made in China