Typically you should first consider the number of appliances you need to power. Next, you need to know how many batteries you want to charge. Having the above information will help you see the number of solar panels you would need to charge and power your RV. However, anything between 400 to 600 watts on average is an excellent idea. A 12-volt battery at 100 AH will work with 300 watts solar panels. So, with two 12 volts batteries, you get 200 to 250 AH and above 400 watts.