We have installed 3 tankless electric water heaters in 3 locations. They work great at the kitchen sink and to the dishwasher. Also good for supplying hot water to a nearby 1/2 bath sink in another location. Have used it in a small cabin for both the kitchen and bath sink as well as a shower in the bath. The sinks work fine but adding the shower was a bit of a stretch. It works but not as consistently as hoped.
Having said that they draw what I would think is too much wattage for an RV. Just use your Gas water heater. We use the electric heater during the day for sink etc, but when we plan on a nice long shower we flip the gas WH switch about 30 minutes before and have plenty of water.
