I am rewiring a house in Mexico and following the 2002 NEC for wire sizing, grounding, circuits, etc for all work from the meter on. Service panel is 125A and will support air condition along with all other lighting and appliances. The utility company will only supply a 6 AWG overhead triplex aluminum service drop cable (87' in length), which does not meet NEC minimum sizing and support 125A load. I can pay a few hundred dollars for larger wire (1/0), which will supply all the necessary current. What effect will the under-sized service drop cable have on the AC compressor, motors and other appliances when the draw is at 100-125A, or is it worth purchasing the larger cable? I would appreciate the pros and cons.
Thanks

The utility company will only supply a 6 AWG overhead triplex aluminum service drop cable (87' in length), which does not meet NEC minimum sizing and support 125A load.
The utility does NOT follow the NEC. They have their own codes and only answer to themselves.
I see many homes where a 200A service upgrade is done from 100A and the utility leaves the old triplex drop to the house.

The #6 in free air handles more current than in house wiring.
#6 from utility may be OK for 125 Amps, I would make a call to your local Electric Company and see what the limit is.