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How Much Does It Cost to Run Halloween Decorations?

For most yards, less than you would guess. A modest all-LED display run a few hours a night costs under two dollars for the whole month of October. A bigger yard with an inflatable, older incandescent light strings, and a projector runs closer to fifteen dollars for the season. The cost comes down to one line: take the total watts of everything you plug in, multiply by the hours you run it and your electricity price, and that is your bill. The worked examples below do the math, and there is a bonus: the exact same total-watts number that tells you the cost also tells you whether you have overloaded the circuit, so adding it up is worth doing for two reasons.

Want the load side, not just the cost? Run the total watts and your cord length through the Extension Cord Voltage Drop Calculator to confirm the far end still gets full voltage and the circuit stays under its amp limit. The watts you added up for the bill are the same watts that keep the display safe.

The formula

Electricity is billed by the kilowatt-hour (kWh), which is 1,000 watts running for one hour. So the cost of a display is:

kWh = (total watts ÷ 1,000) × hours per night × nights

Cost = kWh × your price per kWh

You need three things: the total watts of everything plugged in (read the tag on each prop, or multiply its amps by 120), how long it runs, and your electricity rate. That rate is printed on your power bill. As a stand-in, the U.S. residential average was about 17 cents per kWh in 2025, per the U.S. Energy Information Administration; some states run well above or below that, so use your own number when you have it.

Worked example: a modest LED display

Say you run eight LED light strings at about 5 watts each, plus two LED spotlights at 10 watts each, five hours a night for all 31 nights of October:

Total watts: (8 × 5 W) + (2 × 10 W) = 40 W + 20 W = 60 W

Hours: 5 per night × 31 nights = 155 hours

kWh: (60 W ÷ 1,000) × 155 = 9.3 kWh

Cost: 9.3 kWh × $0.17 = $1.58 for the month

Under two dollars. LEDs sip power, so a lights-only display is close to free to run no matter how many strings you hang.

Worked example: a bigger mixed yard

Now add the power-hungry props. An inflatable's blower runs the whole time, older incandescent strings draw far more than LEDs, and a projector adds a bit more:

Inflatable blower: 250 W

Six incandescent light strings: 6 × 40 W = 240 W

Projector: 60 W

Total watts: 550 W

kWh: (550 W ÷ 1,000) × 155 = 85.25 kWh

Cost: 85.25 kWh × $0.17 ≈ $14.49 for the month

About fifteen dollars. Still not a budget-buster, but you can see where the money goes: the inflatable and the incandescent strings, not the LEDs. Run it fewer hours a night, or put it on a timer, and the figure drops in direct proportion.

LEDs are most of the savings

The single biggest lever on the bill is LED versus incandescent light strings. The U.S. Department of Energy notes LED holiday light strings use far less energy than incandescent ones, on the order of a small fraction of the wattage for the same length of string. A 100-count incandescent mini string draws roughly 40 watts; a comparable LED string draws only about 5 watts. Over a month of nightly running that gap is most of the difference between the two examples above. If you are weighing the swap, the LED-versus-incandescent guide walks through it, and the wattages here are stated examples; your own boxes will list the real figures.

The same number keeps you safe

Here is the part worth the effort. The total watts you added up for the bill is the same figure that tells you whether the circuit is overloaded. Divide total watts by 120 volts and you get amps, and a household circuit has a hard limit on amps. Decorations run all evening count as a continuous load under the National Electrical Code (NEC), and a circuit should carry no more than 80 percent of its rating for one:

15-amp circuit: 15 A × 0.80 = 12 A = 1,440 W ceiling

The 550 W display above: 550 W ÷ 120 V ≈ 4.6 A → fine on one circuit

But go all-incandescent and pile it on, and the cost creeps up while the circuit quietly runs out of room:

Twenty incandescent strings: 20 × 40 W = 800 W

Inflatable blower: 250 W

Fog machine: 1,000 W

Total: 2,050 W ÷ 120 V ≈ 17.1 A → over a 15-amp circuit

Incandescent costs more to run and overloads the circuit sooner, the same choice punishing you twice. Spreading a big display over more than one circuit, and not treating an outdoor splitter as extra power, is how you keep the load safe. The decorations-per-outlet guide covers budgeting a single circuit in full. If your display genuinely needs more power than one circuit can carry, the fix is another circuit, which is a licensed electrician's job, not a bigger breaker.

The short version

  • The formula: (total watts ÷ 1,000) × hours × nights × your price per kWh.
  • Modest LED display: roughly a dollar or two for all of October.
  • Big mixed yard: ballpark fifteen dollars, driven by the inflatable and incandescent strings.
  • Use your own rate. It is on your bill; the 2025 U.S. average was about 17 cents per kWh.
  • The same total watts is your safety check. Divide by 120 for amps, and stay under 12 amps on a 15-amp circuit.

NEC and data reference

NEC 2020. The 80 percent ceiling for a continuous load comes from NEC 210.20(A) and 210.19(A); a continuous load is one expected to run three hours or more per the Article 100 definition. The electricity price is the U.S. residential average of about 17 cents per kWh reported by the U.S. Energy Information Administration for 2025; rates vary widely by state and change over time, so your bill governs. The LED-versus- incandescent energy comparison follows U.S. Department of Energy guidance on LED holiday light strings. The watts-to-amps and watts-to-kWh conversions are the standard power relationships (watts equal volts times amps; a kilowatt-hour is 1,000 watts for one hour), not code values, and the prop wattages are stated examples; your own nameplates govern.

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.

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