Numerous charts and lists have been published with long lists of appliances and how much power they draw. You are then supposed to add up all the watts, then find out how many hours of sun you get, etc etc.
Mobile, Marine, & RV
An "RV system" (small boat and cabin systems are practically identical) can mean different things to different people. It might be just a small 5-watt panel that keeps the battery charged up between a few trips a year or over the winter.