Christmas lights use very few amps when they're LED. A 100-bulb LED mini strand draws only about 0.04 to 0.1 amps, while a 100-bulb incandescent strand draws around 0.34 amps — roughly 8 to 10 times more. A standard 15-amp household circuit can safely carry about 12 amps under the 80 percent rule, which is thousands of LED bulbs but only a few hundred incandescent ones. Knowing the amp draw is how you avoid tripping a breaker.
Amp draw by bulb type
Amperage is just current, and it follows directly from wattage. The table below shows typical amp draw per 100 bulbs, so you can total your display and compare it to your circuit's safe limit.
| Bulb type | Watts per 100 | Amps per 100 (at 120 V) |
|---|---|---|
| LED mini | 4–6 W | ~0.04–0.05 A |
| LED C7 / C9 | 7–10 W | ~0.06–0.08 A |
| Incandescent mini | ~40 W | ~0.34 A |
| Incandescent C7 | ~350–500 W | ~3–4 A |
| Incandescent C9 | ~500–700 W | ~4–6 A |
The 80 percent circuit rule
Household circuits are rated 15 or 20 amps, but you shouldn't load them to the maximum. For a continuous load like holiday lights, electricians apply the 80 percent rule: use no more than 80 percent of the breaker's rating. That gives you about 12 amps on a 15-amp circuit and 16 amps on a 20-amp circuit. Leave extra headroom for anything already sharing the circuit — an outdoor outlet often feeds several receptacles.
How to convert watts to amps
You don't need to measure anything — the math is one step. Amps equal watts divided by volts, and U.S. household voltage is 120. So a display totaling 240 watts draws 240 ÷ 120 = 2 amps, well within a 15-amp circuit. Read the wattage off each box or the plug tag, add them up, divide by 120, and compare the result to your 12-amp (or 16-amp) safe limit. For the wattage side of the equation, see how many watts LED Christmas lights use.
How many bulbs fit on one circuit
Put the numbers together and the LED advantage is stark. At about 0.05 amps per 100 LED bulbs, a 12-amp budget theoretically allows tens of thousands of LED bulbs — far more than any normal display. Incandescent is the opposite: at 0.34 amps per 100, a 12-amp budget tops out around 3,000 to 3,500 bulbs. In real installs the limiting factor for LEDs is almost always the maximum connected sets printed on the plug, not the circuit. See how many Christmas lights you can string together and how many LED Christmas lights on one circuit.
Why a breaker or GFCI keeps tripping
Two different faults cause two different trips. A standard breaker trips when the circuit exceeds its amperage — the fix is to move strands to another circuit or switch to lower-draw LEDs. A GFCI outlet trips when it senses current leaking to ground, which usually means moisture in a connector or a damaged strand. If a GFCI keeps tripping, dry out the connections, elevate the plugs, and inspect for damage before resetting.
How to avoid overloading a 15-amp or 20-amp circuit
The goal is simple. Never overload the circuit. Stay under 80 percent of its rating. That is about 12 amps on a 15-amp circuit. It is about 16 amps on a 20-amp circuit. Leave headroom for anything else already plugged in.
Here is the quick method. Total the watts of every strand. Divide by 120 volts to get amps. Compare that number to your 12-amp or 16-amp limit. If you are close, split the display across two outlets on different circuits. LED strands make this easy, since they draw so little. Incandescent strands overload a circuit far sooner, so they need more outlets. When in doubt, spread the load rather than stacking it on one plug.
Cutting your amp draw? See the best LED Christmas lights. Related: how much electricity Christmas lights use and the Christmas Lights 101 & Safety hub.