We primarily dry camp most of the summer and sometimes Dec. and Jan. in AZ. Our current solar is 300 watts portable and I'll be adding 200 watts to the roof. The portable set up uses 25 feet of 8 awg marine grade wire and has been in service since 2012 on a previous TT and now our Axis.
With 12 volt dc systems voltage loss is the problem and the usual fix is larger wire.
We went with 3 100 watt panels for the portable system because it is easy to handle. At 2X3 feet 17 LB panels aren't heavy just awkward to handle.
Check here for general guide lines:
RV Electrical
Just as detailed as HandyBob's blog but doesn't have the rant.
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