I did a lot of the same thing. I used a bosch 4 gallon point of use, mini tank (electric). I too used only hot water side. The only thing I used hot water for is showers, and I take fast showers. It stays hot through the entire time and recovers fast even though it is electric. I cook with the microwave, and the refrigerator is all electric. With the 26 gallon tank on my generator, I can be totally independent for days without propane.
One extra, when connecting the hot side alone, make sure you cap the cold side. I accidentally opened the cold valve on the shower and the hot water leaked out the cold side. It's all fixed now.
Doc Weaver '98 Freightliner FL60 pseudo toy hauler