What is the electrical voltage / amperage drop on long underground runs.?

Ok first of all I would go with the 100 amp panel, that way you will have all the power you will ever need out there. You have two choices for 100 amps that far out. If you use # 3 wire your voltage drop is 4% if you use #2 its 3.2% the max you are allowed is 5% don't cheap out and use #4 that will have 5.1% voltage drop, while that's "almost" legal its not worth it. If you go with a 60 amp panel use # 4 that will give you 3% voltage drop. Voltage drop is figured by taking 2x12.9 x length x amps then divide that by the circular mils of the wire, then divide that by the voltage. Ok so using #3 wire use the formula 2x12.9x200x100=516000/52620=9.806/240=.0... move the decimal point 2 places that gives you 4.08% voltage drop. Number 3 is fine for 100 amps, but here is a little secret most electricians don't know. The less voltage drop there is the less money you spend on electricity. Most of the money you spend on your electric bill is due in fact to the wires acting as resistors and ...  more