What gauge extension cord should I use for a sump pump?

Use a 12-gauge (or thicker) extension cord for your sump pump. Most sump pumps pull 6–10 amps with a higher startup surge, and a standard 16-gauge cord drops voltage, causing the motor to run hot and fail early. For runs up to 100 feet, go with 12-gauge; for longer runs, use 10-gauge. Always choose an outdoor-rated, three-prong grounded cord—never a two-prong or cheater plug.