How Many Amps of Halloween Decorations Can Go on One Extension Cord?
Keep the total load under 12 amps on a standard 15-amp household circuit, or under 16 amps on a 20-amp circuit. That is 1,440 watts and 1,920 watts respectively. Add up the wattage printed on every inflatable, light string, and prop plugged into that one cord or that one outdoor outlet, and stay under those numbers. With LED lights you can run a lot before you get close. With older incandescent strings you hit the limit fast. The worked example below shows both.
Running a long cord to a far corner of the yard? Check it on the Extension Cord Voltage Drop Calculator. A cord that is too long or too thin loses voltage before it reaches the blower, and that makes the motor run hot even when the amps look fine.
The number you are working toward
A standard wall outlet in the United States is 120 volts. Watts divided by volts gives you amps, so a 120-watt decoration draws 1 amp. Most homes have 15-amp or 20-amp branch circuits behind those outlets. You do not get to use every last amp, though. Holiday and Halloween decorations stay on for hours at a stretch, which the National Electrical Code (NEC) treats as a continuous load, and a circuit should only be loaded to 80 percent of its rating for a continuous load.
15-amp circuit: 15 × 0.80 = 12 amps = 1,440 watts
20-amp circuit: 20 × 0.80 = 16 amps = 1,920 watts
Those are the practical ceilings. Note that this is the whole circuit, not just the one outlet. One 15-amp circuit often feeds several outlets, and sometimes rooms you would not expect, so a heater running indoors can already be eating into the budget before you plug in a single pumpkin. If you are not sure which outlets share a circuit, flip one breaker off and see everything that goes dark.
What your decorations actually draw
The load depends far more on what kind of lights you use than on how many strings you hang. Rough figures, taken from typical product labels:
| Item | Typical watts | Amps at 120V |
|---|---|---|
| LED mini light string | about 5 W | 0.04 A |
| Incandescent mini string (100 ct) | about 40 W | 0.33 A |
| Incandescent C9 string (25 bulbs, 7 W each) | 175 W | 1.46 A |
| Large inflatable blower | about 250 W | 2.08 A |
| Small fog machine | about 400 W | 3.3 A |
The gap between LED and incandescent is enormous. An LED mini string sips around 5 watts, so you could run dozens before the amps add up. A single 25-bulb C9 incandescent string at 7 watts a bulb is 175 watts on its own, which is why the box on incandescent lights tells you to connect only a few strings end to end, often three to five, while LED boxes let you chain many more. Always read the maximum-connection number printed on the package. It is there because the thin wire in the string can only carry so much current before it overheats, no matter what the wall outlet could supply.
Worked example: two displays, same yard
Say you want two inflatables, some string lights, and one animated prop, all fed from a single outdoor outlet on a 15-amp circuit. The all-LED version fits with room to spare:
2 inflatables × 250 W = 500 W
10 LED mini strings × 5 W = 50 W
1 LED animated prop = 40 W
Total: 590 W ÷ 120 V = 4.9 amps
At 4.9 amps you are well under the 12-amp ceiling. Now build the same display with old incandescent strings, spread across a few outlets on the same circuit, and add a fog machine:
2 inflatables × 250 W = 500 W
8 incandescent C9 strings × 175 W = 1,400 W
1 fog machine = 400 W
Total: 2,300 W ÷ 120 V = 19.2 amps
At 19.2 amps this trips a 15-amp breaker immediately, and it is over the 16-amp working limit of a 20-amp circuit too. The fix is not a bigger extension cord. It is spreading the load across two or more separate circuits, or switching the incandescent strings to LED. If the breaker keeps tripping, that is the circuit telling you it is overloaded. Do not swap in a larger breaker to stop the trips. The breaker is sized to protect the wire in the wall, and a bigger one lets that wire overheat.
Amps are only half the story on a long cord
Staying under 12 amps keeps the breaker happy, but a long, thin extension cord has a second problem: it loses voltage along its length. By the time the power reaches an inflatable 100 feet away on a skinny 16-gauge cord, the blower motor may be seeing noticeably less than 120 volts. Motors respond to low voltage by drawing more current and running hotter, which shortens their life and, in a wet yard, is exactly the kind of stress you do not want. A thicker cord (a lower gauge number) or a shorter run fixes it. Run your gauge and length through the extension cord voltage drop calculator to see whether your cord holds voltage over the distance, and read whether your outdoor outlet needs a GFCI before you plug anything in outside.
Quick rules that keep you safe
- Add up the watts, then divide by 120. Keep the total under 1,440 watts on a 15-amp circuit, 1,920 on a 20-amp circuit.
- Obey the string limit on the box. Never connect more strings end to end than the package allows, even if the outlet could supply more current.
- Use one properly sized cord per run. Chaining several light cords together adds up the length and the voltage loss, and adds a failure point at every connection.
- Never replace a tripping breaker with a bigger one. A breaker that keeps tripping is doing its job. Move some load to another circuit instead.
- When in doubt, call a licensed electrician. If you need more outdoor capacity than your existing circuits can give, a dedicated outdoor circuit is the right answer, and it is not a do-it-yourself job.
NEC reference
NEC 2020. The 80 percent ceiling for a continuous load comes from NEC 210.20(A) and 210.19(A), where a continuous load is one expected to run for three hours or more, which decorative lighting on for the evening clearly is. Circuit and outlet amp ratings follow the branch-circuit rules in Article 210. Wattage figures for lights and blowers are typical product values, not code values, and your own labels are what count.
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.
Get the full guide
NEC Code Quickstart
This guide covers one calculation. NEC Code Quickstart walks all twelve exam calculations start to finish, each with a worked example and the exact code reference: ampacity and derating, breaker sizing, voltage drop, box and conduit fill, grounding, dwelling load, range and dryer demand, motor circuits, and transformer current. Written for the 2023 NEC with notes for the 2026 edition.
Related
- Holiday Circuit Map and Load Worksheet (free PDF): a fill-in circuit map for your own house plus six one-page seasonal safety cards, with every load already converted to amps.
- Extension Cord Voltage Drop Calculator: check whether a cord holds voltage over its length and load.
- Do Outdoor Halloween Decorations Need a GFCI Outlet?: the shock-protection rule for anything plugged in outside.
- Wire Ampacity Calculator: how much current a given conductor can safely carry.