This number of bulbs installed depends on the number of wattages; for low watts bulb, you will use more, but higher watts bulb, you will install a few. Let’s find how many watts you can run on a 15-amp circuit. First, we have to find the capacity of the circuit. As the circuit is 15 amps and functions under a potential difference of 120 Volts, the circuit’s power is 15*120 or 1800 Watts. The 120 volts mainly apply in the USA and Canada. Most electricians recommend that you use 80 percent of the total capacity; this is the circuit’s maximum safe load. It improves safety and efficiency by giving a gap in case of power spikes. The National Electrical Code doesn’t specify the maximum number of lights you can install on a 15-amp circuit. The code usually rates lighting as continuous and non-continuous duty load. For continuous loads, NEC limits a circuit breaker’s load to 85%. This rule allows you to calculate the actual number of lights based on their wattage. To get the total number of lights per circuit, you need to calculate lights amp draw. The current draw of each light is the number of wattages divide by 110 volts. For example, a 65-watt bulb would draw 65 divided by 110, which is approximately 0.6 ampere. So, for a 65-watt bulb, you will install around 21 bulbs per circuit. Depending on your house wattage, if you are in the USA (120) or the UK, which is (240), you will still apply the formula. Check this too: Troubleshooting Christmas Lights: Common Problems and Fixes The number of lights to install in a 15-amp circuit depends on their wattage. You will install few bulbs for a higher wattage bulb, and for less wattage, you will install less. The electrician rule of using 80% of the circuit’s power prevents circuit overload, ensuring its efficiency and safety.
