5 Things to Know About Using a 10-Gauge Extension Cord for a 75-Foot AC Run

A 10-gauge cord is more than adequate for a 15-amp portable air conditioner at 75 feet. It is actually safer than using a lighter gauge.

Voltage drop is the main concern with long runs. At 75 feet on a 15-amp load, 10-gauge copper wire drops about 3.6% at 120V, well under the 5% threshold where equipment starts to complain.

A 12-gauge cord at the same length would drop nearly 6%, which is too much. Stepping up to 10-gauge avoids this problem.

A 10-gauge cord is rated for 30 amps at shorter lengths, so it handles the startup surge from the AC compressor without issue. This makes it a safe choice.

Make sure the cord is outdoor-rated if needed, has a ground, and is not coiled up while running, as coils trap heat. Do not use a 14-gauge “heavy duty” cord at 75 feet—it is not enough.