Home Improvement

I've been looking into this (along with some other options like tankless) since my water heater is the next major appliances due for replacement.

Depending on the efficiency of your HVAC and water heater; it might still be cheaper to heat twice (water heater makes water hot & inside air cold; then HVAC makes inside air hot & outside cold). If your efficiency at the HVAC stage is more than double (most modern heat pumps give 3x to 4x efficiency; that's both in the water heater and HVAC). It gets a bit complicated; but the short answer is when it's efficient enough the switch between modes for the hot water heater might not be necessary.

Longer answer; is you need to know the difference in performance of the water heater. Ex. your heating costs go from $10/mo with heat pump to $20/mo with electric element (obviously if gas is the alternate heat source that adds another conversion...). If the marginal increase in HVAC cost is less than that $10/mo difference, there's no need to switch the hot water heater between modes!

Undecided (you tube channel) has a few videos covering the basics that are worth a watch if you're starting to look into the topic, but since you've already been doing research, maybe it's all material you know? Quick link: https://www.instagram.com/undecidedmf/p/C4IrcBOsT_p/

Edit adding a better link: https://www.youtube.com/watch?v=abGiNL9IT54&vl=en