Most electrical outlets used for light fixtures and general-purpose electrical appliances are connected to 15-amp circuits. In trying to connect various Christmas lights you may end up with an overloaded 15 Amp circuit. But an overloaded circuit is a disaster waiting to happen as it can damage your wiring or even cause an electrical fire.
On the whole, you can run as many outlets as possible on a 15-amp circuit breaker as long as they do not overload the circuit breaker. However, it is better that the number of outlets on 15-amp circuit breakers does not hover around the circuit breakers’ limits. The National Electrical Code (NEC) recommends keeping circuit breakers’ electrical load at 80%. Going by this, if we limit each outlet on our 15-amp circuit to 1.5 amps, we can have up to eight outlets on one circuit.
Limit the Number of Outlets on a Circuit Breaker
Limiting how many outlets you place on a circuit breaker reduces the chances of overloading the circuit.
Ordinarily, you can have more than eight outlets on a 15-amps circuit breaker. But then, having more than eight outlets opens up the possibility of using more than eight outlets at once. This can cause an overload.
So, say you have 20 1.5-amp outlets on a 15-amps circuit breaker and you use 15 outlets at once. The total load on the circuit breaker will be around 22.5 amps – more than the breaker’s 15-amp limit. This would be an overload for sure and the circuit breaker will break the flow of current.
How Many Christmas Lights Can I Plug in a 15-Amp Circuit?
The number of Christmas lights you can plug into a 15-amps circuit depends on the total wattage of the lights. However, you should try to keep this total below 1440 watts.
Since mains electricity runs on 120 volts, the estimated total wattage of a 15-amp circuit would be: 120 volts x 15 amps = 1800 watts.
Still sticking to the NEC’s 80% rule of thumb: 1800 x 80% = 1800 x 0.8 = 1440 watts. This means we should try to limit the circuit’s maximum output wattage to 1440 watts for the most part.
With the recommended maximum load of 1400 watts, you can now figure out how many Christmas lights you can connect to a single circuit.
When Using Multiple Units of the Same Christmas Lights
For instance, if you have a 100-count Christmas string light with a wattage of 42.5 watts, you can plug as many as: 1440/42.5 ≈ 33 units of the light. For emphasis, you can connect up to 33 units of the 42.5-watt Christmas string light to the same circuit at once.
When Using Different Christmas Lights
In reality, you may use different Christmas lights. So, their power consumption will vary across board. In such cases, you can add the power consumption of all the lights, then use the total to divide 1440 watts. The value you get tells you the number of that set of different Christmas lights you can connect to a 15-amp circuit.
For example, if brand A runs on 40 watts, brand B runs on 38 watts, and brand C runs of 42 watts. If you intend to connect all of them to the same circuit, the total power would be: 40 + 38 + 42 = 120 watts. Then you can connect as many as: 1440/120 = 12 units of all three brands together to a single circuit.
Another way to put it is that you can plug 4 sets of each brand together in a 15-amps circuit.
How Many Christmas Lights Can I Plug in a 1.5-Amp Outlet in a 15-amp Circuit?
Earlier, when talking about how many outlets you should have on a 15-amp circuit, we suggested eight 1.5-amp outlets.
Going by the recommended maximum wattage we calculated for a 15-amp circuit (1440 watts), each 1.5 amp should power no more than 180 watts for extended periods.
With this value, you can now figure out how many Christmas lights you can connect to the electrical outlets of a 15-amps circuit.
For instance, if you have a 42.5-watt Christmas light, you can plug as many as 4 units of that light in the outlet.
Then again, if you have a 40-watt light, 45-watt light, and 42-watt light, you can connect all three of them to the outlet at once since their total wattage is less than 180 watts.
How to Know You Are Overloading the Circuit
Calculating the total power drawn by all the electric devices connected to the circuit can help you know if you are overloading the circuit.
As a general rule, if the total power exceeds 1440 watts and is closer to 1800 watts, you may be overloading the circuit. But then, this depends on how long the load stays in the circuit.
According to the NEC, if a circuit is loaded at maximum wattage for short periods, there should be no problem. The NEC’s definition of a short period is no more than 3 hours.
In summary, if you use a circuit at over 80% for more than 3 hours, you are most likely overloading the circuit. This goes against the electrical code and puts your home’s electrical system at risk.
Instead of overloading one breaker, you can spread the load across the circuit breakers in your electrical panel.
Outlets and Lights on the Same Circuit
You can have outlets and lights on the same circuit. Typically, lights do not consume a lot of power. This gives you room to use other devices on the same circuit as light fixtures. And as long as there aren’t too many devices in the circuit, there should be no problem.
Some large appliances like space heaters are better off on a dedicated circuit. Using them alongside other appliances may cause the circuit breaker to trip.
Can I Connect a 20-Amp Receptacle With a 15-Amp Circuit?
Using 20-amp receptacles on a 15-amp circuit goes against the National Electrical Code. So, while you can connect a 20-amp receptacle with a 15-amp circuit, you shouldn’t.
Connecting a 20-amp receptacle to a 15-amps circuit is potentially unsafe. Depending on how many amps you connect to the receptacle, you may trip the breaker.
For instance, if you connect 18 amps to the receptacle because it can accept up to 20 amps, the breaker will trip off because you’ve exceeded its limits.
There’s no limit to how many outlets you can use on a 15-amp circuit breaker. But to ensure you never overwork the breaker, keep the number of outlets at a total amperage of less than 80% of the circuit breaker’s maximum.