Wife & I have gotten by on a 5 gallon heater. I don't know how she gets clean (short shower) but I more than make up for her. We always ran it on propane. Before trying a swap, try switching to propane just B4 showers. Then back to electric.
We ordered the Hydro-Hot for our new coach, so we don't get the blow-torch water heater. It is either diesel or electric, and some folks say to switch to diesel B4 showers as the electric may not keep up. Same story different fuel; electric water heating is slow.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project