5 Things to Know About Outdoor Extension Cords for Holiday Lights

Use 14-gauge wire for runs over 50 feet Thicker wire (lower gauge number) prevents voltage drop. A 16-gauge cord works for a small string, but for multiple strands or longer distances, 14-gauge handles 50–100 feet without dimming.

Voltage drop makes bulbs dim Thin wire has more resistance, lowering voltage at the end of the cord. For runs over 100 feet, step up to 12-gauge to keep lights bright.

Match the cord’s amp rating to your load Check your lights’ total wattage. A typical 100-bulb string uses about 40 watts; you can run roughly 15 strings on a 15-amp circuit. The extension cord must also handle that load.

Choose outdoor-rated cords Look for “W” or “SJTW” markings. These cords handle cold weather and moisture better than indoor cords.

Buy one cord the right length Avoid daisy-chaining multiple cheap cords. A single properly rated cord is safer and more reliable than a chain of dollar-store ones.