The number of holiday lights a circuit will handle is dependent on a few factors:
How do I calculate my circuits amperage?
If you want to know how many watts of bulbs your circuit can handle, the equation is:
Household Outlets= 120 Volt
Circuits in an Average Home = 15-amp or 20-amp
Household Outlets can handle about 120 volts, and average circuits at home are usually 15 or 20 amps. In order to calculate the number of watts your circuit can handle, use the equation above. Below are two examples:
1. To calculate the number of watts that a 15-amp circuit could handle, you would calculate:
Watts = 120 (volts) x 15 (amps)
= 1,800 watts
80% = 1,440 watts
*Please Note* Never load your circuit to the absolute maximum wattage. The rule of thumb is to load 80% of the wattage to leave room for error, or expansion. So this circuit can only handle 1,440 watts.
2. To calculate the number of watts that a 20-amp circuit could handle, you would calculate:
Watts = 120 (volts) x 20 (amps)
= 2,400 watts
80% = 1,920 watts
Although this circuit can handle an absolute maximum wattage of 2,400 watts, 80% of this circuit can handle up to 1,920 watts.
What if there are other lights or appliances hooked up to the same circuit?
If you are installing Christmas lights to a circuit that also has, for example 5 60-watt lightbulbs, you must subtract the total wattage of the lightbulbs from the number of watts your circuit can handle.
For example, if your circuit can handle 1,440 watts, you must subtract 300 watts from the total. After subtracting the existing lightbulbs’ wattage, you should have a total of 1,140 watts left available. A small string of LED lights may only use 12 watts, so you should be able to string 95 led lights without causing any fire hazard for your circuit.
How did I get 95, as an answer?
Simply divide 1,140 watts by 12 watts, to get the total number of stringed lights that can run safely from your circuit.
I plan on putting up a lot of christmas lights this year!
Generally, holiday lights will inform you on the package instructions, how much power they require. If you have plan to light up the neighborhood with Christmas spirit this year, we suggest that you run separate electrical circuits. This ensures that nothing else will get plugged into the circuit, stealing power away from your holiday lights.