Christmas Lights

Many people think that you can plug in as many outdoor christmas lights into one outlet as you want since they are small. Well, that isn’t quite true.

Christmas lights, just like all lights, pull power from the outlet in a measurement called amps (or amperes, abbreviated as A). Most outdoor outlets can only provide a maximum of 15amps but since many are also providing power to the inside of your house as well (lamps, other outlets, etc.), many outdoor outlets provide MUCH less than 15amps.

Helpful Hint: Even though the outlet is rated for 15amps, never try to pull the full 15amps from it. You risk tripping a breaker or GFCI if you get too close to the maximum output. A good rule of thumb is to only pull about 80% of the maximum or in this case, 12amps.

Speaking of GFCI protected outlets, these are outlets that are designed to trip (turn off) when they sense a short circuit. Most bathroom and kitchen outlets are protected by GFCI breakers or outlets. Also, most outdoor outlets are GFCI protected as well. This means that water getting into your extension cords or lights from rain or dew could cause your lights to go out by tripping the GFCI breaker or outlet especially if you are trying to pull too much power from the outlet.

And now the math

OK, you know that you have a limit to the amount of amperage that you can pull from an outlet but how many amps does a string of christmas lights pull?

  • 100 light string of mini-lights = 1/3amp or .33amps

Well, with 12amps to play with, that means you can have 36 strands of 100 mini-lights. That seems like quite a lot! But you have to count everything. Here are some other items to consider:

  • 60watt light bulb in a blow mold figure = .5amps
  • 15 feet of rope light = .75amps
  • 150watt flood light = 1.25amps
  • 300 light strand of icicle mini-lights = 1amp
  • Inflatables = .5 to 1amp

It adds up quickly!

We need more power Captain!

If you find you are running out of amperage, find another outlet, on a different circuit, to power part of your lights. Or better yet, make the investment in LED lights!

  • 60-70 light string of LED lights = .03amps

Yep, 300 lights of mini-lights pull 1amp but 300 lights of LEDs pull only .15amps! The LED lights might cost a little more but they are safer (don’t get as hot), pull MUCH less amperage and last longer.

Putting everything together

When you assemble your christmas light display, be sure to use only products rated for outdoor use. Yes, they cost more but they are designed to be out in the weather. Rain and dew can be rough on indoor products causing the products to rust and possibly short out causing a shock or fire hazard!

Helpful Hint: When you connect strands of lights together, always use the rule of threes. Don’t connect more than three strands of lights together. The lights aren’t designed for more than that (unless specified) and if you add more, the fuses in the strands might blow.

Many people follow the above rules but forget about their extension cords. Extension cords are measured by their length in feet and the size of wire used in gauge (the larger the gauge number the smaller the wire). The longer the extension cord and/or the smaller the wire, the less amperage can flow through it. Having the wrong extension cord can dim lights, cause inflatables not to work properly and cause a fire hazard from overheating. See our article entitled “What Gauge Is My Extension Cord?” if you need help determining what gauge wire is used in your extension cord.

Ext. cord length Amperage Required
0-2 amps 2-5 amps 5-7 amps 7-10 amps 10-12 amps 12-15 amps
25 ft. 16 gauge 16 gauge 16 gauge 16 gauge 14 gauge 14 gauge
50 ft. 16 gauge 16 gauge 16 gauge 14 gauge 14 gauge 12 gauge
100 ft. 16 gauge 16 gauge 14 gauge 12 gauge 12 gauge 10 gauge
150 ft. 16 gauge 14 gauge 12 gauge 12 gauge 10 gauge
200 ft. 14 gauge 14 gauge 12 gauge 10 gauge

Table courtesy of Planet Christmas

Think of it as a hose. The bigger the hose, the more water will flow. If you need a 50ft extension cord to provide a total of 6.5amps, you need to use a 16gauge or larger extension cord. Extension cords are expensive, matching the right extension cord for your needs could save you quite a bit of money!

Helpful Hint: If you have open outlets on your extension cords (using only two outlets on a three outlet extension cord), be sure to protect the open outlets from rain, dew and snow. If water gets into the extension cord, it could cause a short which will trip your breaker or GFCI protected outlet.


Using the above as a guideline, you can have a beautiful, safe christmas light display. Now, go make your neighbor’s jealous!