Rando,
I basically dealt with the same problem when I decided to go with and electric fridge and solar. As previously stated, its a 'crap shoot'. Its difficult to dial in exactly what you will need since there are so many variables including how, where, when you camp, ambient temps. total available amp hours, solar setup, etc.
My problem solving efforts lean much more toward the 'empirical' approach than the 'scientific' and my friends almost always accuse me of overbuilding. That said, here is the what, and the why of what I did, (and therefore what I recommend) once I decided on an electric fridge and solar.
1. Choose an honest-to-goodness compressor type fridge. Unlike thermoelectric units cooling is not related to the ambient air temp. So lets say you are camping in 90º weather. That thermoelectric unit is going to cool down to around 50º. Sub-optimal. I can only assume you do not enjoy drinking 50º beer any more than I do.
2. Install a lot of battery. I installed (4) 230 amp 6 volt deep cycle batteries. Go with pairs of 6 volt batteries. In testing I have found I can go about 3 days/nights before I start closing in on 12.07 volts if its not too hot out.
3. I went with a 140 watt panel but built a 'solar tracker' based on a cheap collapsible 1.5" PVC stand. Along with just being a lot of fun to muck around with, the tracker keeps the board facing directly into the sun all day.
One last thought on 'overbuilding'... I spent the first half of my life buying cheap, minimum effort stuff. Then after a while having to replace it once it proved to be sub-optimal. Obviously the cost and effort involved was almost always greater than if I would have 'overbuilt' in the first place.




