earlycuyler
Extra long Bad Ass Cut.
I believe the tankless heaters make sense for small in-law units, maybe cabins, rentals, and other places. But when you consider that I heat water for nearly 5000 sq ft with one device for less than $10/month (nat gas) the economy and ecology saving can't be that great. Especially because you have to install multiple devices all over the house and in the US -- most of them are electric not gas.
The efficiency of a tanked water heater is not that bad because heat is stored fairly efficiently. Especially if you add additional insulation to the tank and turn down the temp.. The efficiency comes from "instant on" and not having to run water for a couple minutes to flush the pipe path with hot water. Not a problem with a daily shower or laundry or auto dish washers.
We do about half what you do. 2500sq ft. the kids wash the dishes and we rarely use hot water in laundry. your point is excellent about multiple units being needed, but we have done fine with six people using hot water in our home.