The information in these responses will all be helpful, but I'll add my own 0.02 cents...
I have two 6v GC's and started out with 200w which mostly worked out well, but found that in inclement weather, shorter days, and higher latitudes even another 100w was of great assist (300w total)...My system has now grown to 440w, whatever system you choose be sure and size it for future growth...As far as genny goes (Honda 2000), I really never need it except for very occasional Air Cond use...BTW, Retrofitting to a far more efficient two speed furnace saves regularly about 6 amps.
Best Regards,
3 tons
