Get a 14-gauge outdoor extension cord.

Yes, you want the thicker wire. For holiday lights, a 16‑gauge cord works for a small string, but if you’re running multiple strands or going more than 50 feet, step up to 14‑gauge. That’s the short answer.

Voltage drop is what makes bulbs dim. Thin wire (higher gauge number) has more resistance, so the voltage at the end of the cord is lower. The longer the run, the worse it gets. A 14‑gauge cord handles 50–100 feet without noticeable dimming. For really long runs (100+ feet), go 12‑gauge.

Tripped breakers happen when you pull too many amps. Check the wattage of your lights. A typical 100‑bulb string is about 40 watts. You can run about 15 of those on a 15‑amp circuit before tripping. But the extension cord itself also has an amp rating – match it to your load. Outdoor rated cords (marked “W” or “SJTW”) also handle cold weather better.

Don’t use indoor cords outside. Don’t daisy‑chain five cheap cords together. Buy one properly rated cord the right length.

Your lights deserve better than a dollar‑store cord.