it is unlikely you will dropped the water level in the hot water heater enough to expose the heater element. The hot water comes off the top of the heater tank and the element is below that.
Not sure how you are going to be using the electric element while boon-docking without killing the batteries before you run out of water.
That is what the propane is for.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles