I would like to go the solar route but where do you put a large heavy 60W+ panel? Are they really OK on the roof of a caravan".
Our solution for safe storage and transport was to make a light plywood "cassette" and mount this under the rear of the caravan. This fits nicely between the chassis and its drop-down access door has a locked harps. Our panel is 8kgs and the cassette 3 kgs. This has proved to be a good solution.
They are fine on the roof and throughout the summer, being horizontal has minimal real performance degradation at that time of the year.
Our own need included winter use during which being horizontal has a big detrimental performance impact, hence going for a free standing unit.
On the roof there are two other important considerations; first you must be able to clean it frequently as dust, bird poo etc has a disproportionately big impact on performance.Secondly you need to consider where the shade can fall when placing your van on any site.