Wire sizes become important at low voltages. At 12 volts DC a loss of more than 10% in voltage across the length of the wire can mean the difference between the inverter running or not running. The currents can get high and any voltage drop becomes significant. In general at 12 Volts DC one should run the inverter close to the battery and then pipe the 120 Volts AC to the point of use on smaller wire.
Wire Sizes and Maximum Length Determination
