Conversation from HeatSpring.com NABCEP Entry Level Course
Good explanations of all the details per wire sizing. The altE store and many others have their calculators to sell us wire, combiner boxes, and OCPD’s.
I see most of them default with 2-3% voltage drops max for wire sizing per distance, and inverter wattage.
If your distance is short, you should be very close to 0% voltage drop. It is all relative to the price of the wire and the price of the rest of the PV system. The increased price on 5 feet of wire is much less than the increased price of 500 feet of wire. 500 feet of wire might be a consideration for 3% voltage drop, but 5 feet... Up-sizing that wire would be relatively cheap to consider losing 3% of your energy for 30 years just to save $5.
HeatSpring.com NABCEP Entry Level Course Conversation