[mataug]

> My only regret was going with a Rheem heat-pump water heater in this mix. It does not perform well at all.

Heat-pump water heater's performance depends a lot on where its installed and the airflow+heat available. If the water heater is undersized or if there isn't enough heat in the air, it would perform worse than a standard gas/electric water heater.

Mine is installed in a closet under the stairs, which is not ideal, but as long as I keep the water heater in eco mode, and keep closet door slightly open, it works good enough for our usecase. Our annual water heating costs went down from ~$500 to ~$100 after switching to the heat pump water heater.

[usrusr]

As in the cold end of the heat pump is inside the heated area of the house? That feels very weird. On the other hand with heat pumps, stacking multiple stages strategy isn't necessarily a bad thing! All inefficiencies are not really losses but merely resistive heating contributions (unless their heat escapes to the final cold sink aka outside) and in the end the real question is which configuration is good in terms of capex and maintenance.

In an environment where getting rid of humidity is a concern (mold!), a "cold end inside" heat pump for water might even double as a dehumidifier, with water condensing on the cold end sent to the sewers, contributing a little energy in the process.

[sf_rob]

That's not uncommon and is even beneficial in warmer climates. It will be parasitic in winter (even if externally vented) and symbiotic in summer.