Portable solar panel for motorhome

That is a bit like asking how long is a piece of string? There are too many unknowns. You would be better off sitting down and thinking a  bit more about your needs and the power consumption you use. The best I can suggest is read this guide >here< and use >this spread sheet< to play around with figures to give you some answers. You will also have to think about how you want to connect a portable system to your motorhome 12v system.

peedee