How many watts of solar do you need?
The design of this van will have room for two, 200 watt solar panels. That’s 400 watts. Some vans have 200, 400 or even 1000 watts of solar.
Generating solar will vary with the season ( in winter months the “Solar day” is shorter), location and where you park.
To be safe and ensure that the solar panels meet your expectations multiply by 4. What I mean by this is if you expect to generate 100 Ah of power each day, you need to have 400 watts of solar.
So, I have 300 Ah of batteries, and only expect to generate 100 Ah of electricity from solar each day. If my power usage is more than 100Ah per day I would not keep up with my needs using only solar.
Remember I can also charge from shore power, or the alternator!
For our van the most important item to power is the refrigerator/freezer. It uses 65 watts, or 1560 Wh (65 x 24 hours). 1560 Wh/12 volts = 130 Amp hours. So, If I am using 130AH per day, and only gain 100 watts from solar, I am at a loss of 30AH per day. 300/30 = 10 days. The result is that the van can sit for 10 days on solar power. After that I would need to start the van to charge from the alternator.