You can never have too much solar for your RV!
To make a very general statement, a 100 watt solar panel and a decent solar charger sitting flat on the roof or ground, and you follow the good weather, one can assume (we all know what happens when we assume…) that it will yield about 30AH of battery power. This is a big assumption with solar days ranging from 5 hrs and upwards of 9 hrs depending on the time of year. I won’t get into comparing Alaska and Arizona solar yields. If you tilt your panels, you can expect to get approximately 11-45% more yield depending on distance from the equator.
There are two main types of solar panels, portable and roof mounted. Comparing the two remind me of the tortoise and the hare race.
Portable panels are great as it is easy to track the sun for maximum wattage into your cottage! You will easily beat the norm 30AH per 100 watts of solar panel and you can park your RV in the shade as well. You will not have to get on the roof to install, tilt or wash the panels. The size and amount of solar panels are only restricted by how much you want to move around. The downsides include having to store them somewhere for transport, the wires can be a tripping hazard, wind will be a factor and it is another ‘move day’ chore. Ground panels are more likely to break or maybe even get stolen. They can be a pain if you will not be staying in the same place for more than a few days and they will not charge the battery if you don’t set them up.
Roof panels are awesome because they are always charging your batteries when the sun is up. Believe it or not, some solar installers use VHB tape and don’t drill holes in the roof to attach the solar panels, this is tried and true on most roof types. Once you install them you only need to look at them for inspection and to wash them. You can still tilt the panels on the roof if you choose to. AM Solar sells ’tilt bars’ and they make a measurable difference. The amount of solar panels that you can install are limited by the amount of real estate you have on the roof and you need to account for shading from anything sticking up from the roof. Even a little shade on a panel will stop the production on that panel/string. The panels on the roof will help shade your RV and may be stronger than your existing roof. If you end up with more solar than you can use you can always cook with an induction cooktop, instant pot, heat water, leave a light on or my favorite, share with other boondockers!
The most conservative boondockers will want around 200 watts of solar. The average that I see out here is 400-600 watts. Power hungry boondockers will have north of 800 watts of solar. My recommendation for most starting out boondocking that are not sure how much solar they need would be to get some solar panels that could be mounted on the roof but keep them on the ground. Try them flat on the ground, tilted in the same orientation as your RV and track the sun with them to get an idea of the difference in output where and when you boondock. There is no amount of research that will compare to actual use.