This is the solar set-up that I put on our TM. I went with 200W due to space restrictions on my roof.
General rule of thumb is 1W of solar panel for 1A of battery capacity. If you buy 400W of panels and 205W of batteries (2x Trojan T105 6V golf Cart batteries), you may find that the batteries charge to capacity very quickly and the solar panels are off most of the time. If you go with 100W of solar panel, you may not reach full charge on all but the sunniest of days and little use of furnace, lights etc. 200W seams to be a pretty good balance with ~ 200-225AH of battery capacity.
You may want to try 200W then add to if you find that you need more. It's easy to add to an already existing set up if you start out with a 30A controller.
I have a 2,000W pure sine wave inverter and use it to make coffee in the morning and maybe 5-minutes with the microwave per day. The only exception is if it's cold and I have to run the furnace a lot.
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