Basically I replaced my gas water heater with a hybrid water heater. I couldn't find a way for the reserve water heater to be a hybrid water heater, which is a significant need because the hybrid water heater draws very little power when it runs (meaning my 9 kW inverter has plenty of power leftover to power other appliances without pulling from the grid even when the hybrid water heater is running). Plus I vent the air intake of the water heater from the attic (hot air) so the heat pump on the water heater doesn't have to work hard to find heat in the air to transfer to the water.
Another reason I went the hybrid water heater route is I wanted to vent the cold air into our living quarters. The idea is to be a two-fer: heating water while cooling my house, which I need done 3/4ths of the year, so it reduces my A/C use.
It sounds like a well thought out system. I’d almost cut down my trees to have one!
An old story - I had a job with a company doing solar hot water retrofits, and finally talked my dad into putting one on his house. With the tax breaks, it was cheap but still he wasn’t sold on it.
So, he kept a record on electric bills over the next year or so, and he was proud to declare that his son’s crazy solar contraption actually DID save money! He became our best salesman and had to show everyone how it well it worked.