[rsync]

Let’s say you have a 5BR house … it has been 2-3 years since I surveyed the options but at the time, tankless water heaters that were electric maxed out at something like 6gpm ?

As opposed to a fairly standard 12gpm for a gas unit.

So … you’d have to either take a major step backwards and use a tank heater… or … maybe duplex two units in parallel…

FWIW, I looked into this because I wanted to use an electric option but it’s just not practical.

[Karrot_Kream]

Heat pump water heaters are what you're looking for. They're still tanked so don't need as much instantaneous power to heat a large body of water which also makes them amenable to batteries as a backup. As a bonus, in California water heaters are often installed in garages for townhomes and detached houses and the heat pump will end up cooling the surrounding space which tends to be a benefit during the summers and isn't a big problem through our generally mild winters.