Display kWh cost
Estimate season electricity use and cost from total display watts, hours per night, nights, and your $/kWh rate.
kWh = total_watts × hours_per_night × nights ÷ 1000 · cost = kWh × rate
When to use
Use this when you want a season kWh and dollar estimate before you add more LED eaves, blow molds, or inflatables. Enter total display watts, hours per night, nights in season, and your electricity rate ($/kWh).
Estimate season electricity use and cost from those inputs. Pair it with timer zone count and timer-on-hours tools if you will stagger zones instead of running everything from dusk to midnight. Keep nameplate watts honest — packaging “equivalent” claims are not the same as draw.
Stop and ask a licensed electrician when loads, hardwired outlets, or roof work go beyond temporary plug-in holiday displays. Utility taxes and tiered rates are not modeled here.
Worked example
Example: 500 W × 6 h/night × 45 nights ÷ 1000 = 135 kWh. At $0.14/kWh → $18.9.
Timers and weather cut real hours; this page models the arithmetic you enter, not utility taxes.
Season examples for Prince William County displays
Christmas, timer-controlled. Lights up on the Friday after Thanksgiving and down on New Year’s Day is about 36 nights. A mixed display of 300 W of LED strands plus two inflatables at 150 W each totals 600 W. On a 5-hour timer (5 to 10 PM): 600 × 5 × 36 ÷ 1000 = 108 kWh, or about $16.20 at $0.15/kWh.
Swapping old C9 bulbs. One hundred incandescent C9 bulbs at 7 W each draw 700 W; one hundred LED C9 bulbs at about 0.6 W draw 60 W. Over the same 36 nights at 5 hours, that is 126 kWh versus 10.8 kWh — roughly $18.90 versus $1.62 at $0.15/kWh.
Halloween month. A 400 W Halloween setup with fog lighting, projectors, and string lights, on 4 hours a night for the 31 nights of October: 400 × 4 × 31 ÷ 1000 = 49.6 kWh, about $7.44 at $0.15/kWh. Fog machines heat in bursts, so use their average draw from the manual, not the heater’s peak.
For your rate, look at the per-kWh charges on your electric bill (Dominion Energy or NOVEC in most of the county) and add the energy, fuel, and delivery charges together. A whole-bill average — total dollars ÷ total kWh — is a good single number to enter.
Limits / assumptions
Assumptions: inputs match the hints (measured eaves, nameplate watts, package strand length, and so on). Terms not named in the formula are not secretly included.
Limits: outdoor weather, GFCI trips, and real stock sizes vary. Prefer outdoor-rated cords and clips; ladder and roof work need their own safety practices.
Responsibility: confirm safety-critical electrical and height decisions with manuals and, when needed, a qualified professional. PWC Lights does not stamp displays.
FAQ
How do I total the watts?
Add nameplate watts for lights, inflatables, projectors, and controllers that run together.
Where is my $/kWh?
Your utility bill lists an energy charge per kWh; use that instead of a national average when possible.
Does a timer change the math?
Yes — shorter hours cut kWh linearly. Enter the hours the timer actually allows.
LED vs incandescent?
Use the LED watt savings calculator to compare two watt totals side by side.