For electric I think that it is a non-starter for RV and most would use 15 amps or so on 120VAC.
Even at the limit of 120 volt system it would have limited temperature rise.
I use a Fastar LP gas unit and it will provide all of the hot water you can use.
I think it is lighter since it doesn't have 6 gallons of water in it all the time although it may be slightly heavier than a tank heater.
I did have to replace my unit for another $80.00 due to water getting into the system on the road.
I found a fair amount of corrosion in the little battery
compartment and I broke one of the metal springs that connects to the D cells.
After I replaced it with my spare I checked the power switch that I had forgotten about also on the bottom.
I found that it had high resistance and turning it on an off a few times brought the resistance right down.
It is possible that is all I would have had to do to fix the unit IF I HAD THOUGHT OF IT at the time.
Here is a picture of my setup on the extended tongue of my 16' Scamp
. I fabricated the SS and Lexan enclosure, but I have seen other units just mounted in the open and they seem to work OK as well.