How many Christmas lights can you run on a circuit?

How many Christmas lights can you run on a circuit?

In this post we’ll show you how to calculate the various estimates needed to ensure your decorations follow the best electrical practices. There are three parts to think about for your Christmas decorations’ electricity consumption: How much electricity can your wires, circuits, and bulbs conduct?

What are Wire Gauges?

Wire gauge refers to the diameter wiring. The lower the gauge, the thicker the wire. Low gauge wire conducts more electricity. Mini lights use 22 gauge wire. C7s and C9s generally use 18 gauge wire. Specialty bulbs have a large base that requires them to be on 12 gauge wire.

Heavier wire is usually more expensive, but it can support many more amps. Check the wire’s amperage rating for the maximum amps you can run through it. A 22 gauge wire typically supports 3 amps, 18 gauge wire is good for 6 amps, and 12 gauge wire supports up to 20.

How many lights can you safely string together?

Always check the wire and its packaging for any indication of how many lights you can chain together. Even if your wire gauge is rated for many more amps than you may be using, it’s wise to follow the instructions. In situations where there is no indication of how many lights you can string together, you’ll certainly want to play it safe and not come anywhere close to maxing out the wire’s amperage.

To answer the question, calculate the total amperage for how many bulbs you have by using the electrical load calculator. If you have not purchased lights yet, you have the added benefit of being able to work backwards. Instead of entering how many bulbs along with their wattage/voltage into the calculator, you can enter your maximum amperage (this is the wire gauge’s amperage-rating) and the calculator will tell you how many bulbs you can use. Use a lower amperage than the gauge is rated for to add further safety measures.

Category Bulb Type Watts Volts
C7 LED 0.4 120
Incandescent 5 130
Incandescent 7 130
C9 LED 0.65 130
LED 0.65 230
Incandescent 7 130
Rope Light LED .07 120
Incandescent .33 120
Mini Light LED C6 Strawberry .07 120
LED 5MM Wide Angle .01 120
Incandescent .4 120
Specialty LED A19 3 120
LED F15 1 120
LED S14 1 120
Incandescent A19 25 120
Incandescent F15 40 120
Incandescent S14 11 120

Circuit Ampacity

Next you need to know what your circuit can support. Most homes have circuits that support up to 15 or 20 amps. The circuit breaker will have exact circuit amperage information.

United States homes have about 4 wall outlets connected to the same circuit, which could add up to 8 potential wall sockets to connect lights to at the same time, each of which can have their own string of lights. The easiest way to determine which outlets are connected to which circuits is by plugging lights in and flipping the breaker.

Outlets generally conduct 120 volts of electricity. Multiplying the circuit’s ampacity by the outlet’s voltage gives us the maximum total wattage that can be supported for that circuit. In a 15 amp circuit, the total wattage is 1,800 watts, and a 20 amp circuit supports up to 2,400 watts.

To remain under the circuit’s maximum capacity, add up either the total wattage or amperage of each holiday lights display connected to the circuit’s outlets. You can use the electric load calculator to determine total wattage/amperage for strings of lights or large Christmas decorations.

Outlet vs. Bulb Voltages

One final note regarding voltage is that your outlets conduct electricity at their given voltage, while bulbs are rated for a maximum voltage. All bulbs that are 130V can take up to 130V of electricity. Since that’s greater than the outlet’s voltage, they’ll be completely compatible.

The noteworthy downside of having different voltages between bulbs and outlets is that a high voltage bulb should be paired with a high voltage outlet for best visibility. A 230V bulb used in conjunction with a 120V outlet will look dim. Meanwhile plugging in a 120V bulb to a 230V socket will always blow out the strand of lights. Remember, you can’t change the socket’s voltage, but you can change the bulb’s.


Ultimately, there are several limiting constraints to work around when trying to determine how many Christmas lights you can use. Circuits are the largest constraint, then outlets, then the wires. As long as you have more outlets connected to new circuits, you can continue adding lights. Once you run out of free outlets, you’ll have to start stringing lights together, which then causes you to look at the wire gauges for their amperage-rating. If you use too many outlets on the same circuit or connect too many light strings together, you’re also at risk of overloading the circuit. All of these potential electricity issues intertwine with one another and they’re each important to consider when asking yourself how many Christmas lights you can use.

The question at the end of the day is always how many Christmas lights can you use per circuit. With each new circuit comes a new opportunity to overload it.

Altogether you’ll need to keep your holiday display under each circuit’s maximum ampacity and every string of lights also needs to be below its maximum amperage-rating for its wire gauge. With a major holiday decoration installation, that can be a lot of moving parts to keep track of. We created the electrical load calculator to help you quickly identify areas of safety concern. Additionally, you can evaluate the cost of running LEDs vs Incandescents with our electricity bill calculator.


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