You've got it right, but I think you may be over estimating how much power you'll get in overcast conditions. Most reports I've seen for non-thin film PV modules would seem to indicate that you can expect around 10% of the PV module's rated output in overcast.
Originally Posted by pods8
I'd look for people in your area who have some solar installed and see if I could find out what they are getting in the real world in your area.
Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker