Electric heating uses too much power and would drain a single battery after just a few heating cycles.
I had a electric shower water heater that worked very well in the sold Sprinter. System consisted of these parts:
1. A 600 watt pure sine inverter powered by the Sprinter 12 volt system.
2. A 5 gallon SS beer keg.
3. A 425 watt (6 gallon) RV conversion kit to convert a RV propane heater to electric.
4. A inside shower enclosure.
https://www.walmart.com/ip/Leisure-...0&wl14=rv water heater conversion kit&veh=sem
Had to drive the vehicle for about 45 minutes to obtain 5 gallons of 90 degree water in the keg. A cylindrical 12 volt DC pump was installed in the tank and that was connected to a garden hose with a on/off nozzle. All the water in the keg was at the correct temperature so no hot/cold water mixing required and no plumbing needed. The 90 degree temperature setting for the thermostat was determined by taking a bucket into the shower at home and measuring the temperature I like.
Simple system since I already had the inverter that was used as a backup method of charging the house battery. Primary method of charging the house battery was a 205 watt solar panel with a MPPT charger.
Disadvantage was you had to drive the diesel Sprinter because they should not be idled.
So based on the Sprinter system I have made some improvements for the Transit build:
1. Bought a 625 watt (10 gallon) RV conversion kit.
2. Eliminated the beer keg and replaced it with a custom 14 ga. SS tank that is also the support pedestal to bring the portapotti up to the correct height. Used the wasted space under the toilet.
3. Bought a gas Transit so I can idle the engine to heat water instead of driving.
4. Changed from a 205 watt solar panel to a 300 watt panel. Will now have excess solar power.
5. Revised the electrical so I can heat the water from shore power or from the vehicle powered inverter or from the house battery/inverter.
6. Added a indicator light that is on when water is heating and off when thermostat stops the heating.
7. Made the shower enclosure a multipurpose enclosure. When not used as a shower the enclosure has the portapotti at the bottom, a pivotable/removable bottom shelf, two storage containers on the bottom shelf, a pivotable/removable upper shelf that doubles my counter space and 3 removable towel rods at the top. Rods, containers and the two shelves are removed to make it into a shower.
So heating water electrically works.
The improvements should heat the water in about 30 minutes. Will not waste space with the beer keg, can heat water without driving on clear days to heat the water without engine running. Using the house 255 amp-hr battery will deplete it down to about 90% SOC so should get back to 100% in a day of clear weather.
Waiting for the water tank before I can complete the Transit install. Tank has been laser cut and formed and is now at the welders. Should be able to post some pictures soon.