I am just now thinking about SOLAR PANELS for my off-road camping setup. I think you must go the baby steps way first to find out what you want to have with you when you are camping off the power grid and have enough installed batteries to support this.
The 120WATT SIZE PANELS only produce around 5-6AMPS DC current during high sun. With this in mind you will need to figure out how many panels you will need to properly re-charge your installed battery bank. 5-6AMPS DC Current is not alot of SUN POWER if you want to re-charge your batteries in a quick three hour charge time.
My on-board charging setup will need to produce 14.4VDC @ around 20AMPS per battery if I want the batteries to re-charge within a 3-hour time frame. The SOLAR PANELS will have to do the same thing. Of course you will have high sun for a good 5-6 hours or so a day so that will be enough to re-charge a couple of batteries to their float mode in the one day sun I would think. This is especially so being in the AZ High sun area to start with having more than 5-6 hours of high Sun..
You should realize that SOLAR is not the only answer and you really have to have a generator setup if you want to totally rely on keeping your batteries at their minimum of 90% charge state when you need to use them.
I am just now in SOLAR PANEL MODE thinking after camping off the power grids for the past few years with my 255AHs battery setup. I know exactly what to expect and when I need to do re-charge my batteries. They are still going good since being installed in 2008. I will most likely start out with two 120WATT PANELS on my POPUP ROOF and maybe add another 250WATT PANEL later on. That is about all the room I have on my POPUP ROOF.
The only real thing I have learned for my style of camping off the power grid is I MUST start each afternoon/evening with a good 90% charge state if I want to make it through the night. This all then gets re-charged again starting at 8AM the next morning. I may also have to run my generator for around one hour to get over high current BOOST MODE. Then I am hoping the SOLAR PANELS here on the East side of the US will take over and get me re-charged to at least to the 90% charge before I start using the batteries again that evening.
This requires a good monitor system to keep me in the know where my approximate battery Bank charge state is when nearing the loss of high sun. I can always go back to generator when allowed to run my generator at the camp site to get the battery bank where it needs to be at. I will not want to start my evening run off the batteries unless they are are at least at the 90% charge state.
These are my baby steps...
Roy Ken