110V water heater
Have you thought about the Flat Plate Heat Exchanger?
It uses hot engine coolant to heat water, on demand. You then don't need to use propane or 110V power to heat the water. The downside is that you need to have the vehicle running.
If you go with the 110V system, you'll either need the big inverter with a big battery bank AND the engine running to heat your water (which you could do while driving to your destination) or you would need to be able to plug into shore power (or generator.) Also, take into consideration that electric water heaters, in general, take a long time to heat up.
I recall some time ago on the SMB Yahoo Group, somebody made mention that they heat the hot water tank in the evening, such as driving to their destination, and that the water is still warm enough for a shower in the morning.
2005 Ford E-350 Diesel Sportsmobile
EB 102 Voyager top, 3.55 rear, Mobil 1 all around
270 amp alternator, billet water pump, coolant filter kit,
aluminum radiator, X-Monitor with pyro, trans temp, boost
+ Scan Gauge & SCT Live Wire (Economy)