Vtmaps' and others' suggestions are correct - know your loads. However, 800W of panels on an RV roof probably won't generate as much power overall as the same amount of panels on a house roof, because RVs often are not oriented ideally to the sun or are partially shaded. For this reason alone, I suggest carpeting your roof with as many panels as will fit! PV is still cheap, so a few more panels aren't much more in the context of what the RV will cost you anyway. Just don't put panels next to roof-mounted A/Cs or stink pipes or fridge vents or whatever sticks up above the roof - even the slightest partial shading such as from RV roof impedimenta will drastically reduce their output. If you can mount your panels on tiltable mounts they will produce slightly more power in the summer but probably appreciably more power in the winter when the sun is lower. 1000W of panels is about the most that a charge controller can handle for a 12V system (which your RV is). If you can charge your batteries at a 10 to 13% charge rate they will charge quickly, maybe allowing you to also power opportunity loads in the afternoon after they're fully charged, such as power tools or a washing machine or other non-time-sensitive but power-hungry loads.