Christmas Lights Electricity Cost Calculator: LED vs Incandescent
Defaults are the U.S. Department of Energy figures for a 100-lamp mini string: 0.4 W per incandescent lamp (40 W) and 0.04 W per LED lamp (4 W). Your package lists the real number, so replace these if you can. Larger bulbs such as C7 and C9 use more.
Default: 18.31 cents, the U.S. average residential price for July 2026 (U.S. Energy Information Administration, Electric Power Monthly, released September 24, 2026). Your bill shows your own rate.
How it is calculated
Cost = strings × watts per string × hours per night × nights ÷ 1,000 × price per kWh. For example, 12 strings of 40 W lights for 6 hours on 40 nights is 12 × 40 × 6 × 40 ÷ 1,000 = 115.2 kWh, which is $21.09 at 18.31 cents. The same 12 LED strings at 4 W use 11.52 kWh and cost $2.11.
For a sense check, the Department of Energy says lighting a 6-foot tree for 12 hours a day for 40 days costs about $0.27 with LEDs versus about $10 with incandescent lights, and that LED strands use about 70% less energy than conventional strands.
Data last verified: October 9, 2026. Wattage defaults: U.S. DOE niche lighting report (2003 data, so recent LED sets can differ) and Energy.gov. Price: EIA Electric Power Monthly, July 2026 data. Energy prices change every month.
Educational estimate. Real use depends on the exact lights, timers, dimming and your utility's rate plan, which may include fixed charges and tiers. This tool does not include the purchase price of lights or replacement bulbs.
Find out what your string lights cost to run this season and how much you would save with LED sets, using Department of Energy wattage figures and the latest U.S. average electricity price you can overwrite.
How it works
- Enter the number of strings, the watts per string and how many hours and nights they are on
- Keep the U.S. average price or type your own cents per kWh
- Compare the season cost of incandescent and LED strings and see the savings
Frequently asked questions
How many watts does a string of Christmas lights use?
It depends on the bulb type. The U.S. Department of Energy's niche lighting report estimates 0.4 watts per incandescent mini lamp and 0.04 watts per LED mini lamp, which is about 40 W and 4 W for a 100-lamp string. Larger C7 and C9 bulbs draw more, so use the watts printed on your package when you can.
How much cheaper are LED Christmas lights?
Energy.gov says LED strands use about 70% less energy than conventional incandescent strands, and gives the example that lighting a 6-foot tree for 12 hours a day for 40 days costs about $0.27 with LEDs versus about $10 with incandescent lights. The DOE niche report's per-lamp figures imply savings up to 90%.
What electricity price is the default?
18.31 cents per kWh, the U.S. average residential price for July 2026 from the U.S. Energy Information Administration's Electric Power Monthly (Table 5.6.A, released September 24, 2026). Prices vary by state and month, so use your own rate from your bill.
How do I work out the cost myself?
Multiply watts by hours and by nights, divide by 1,000 to get kilowatt-hours, then multiply by your price per kWh. Twelve 40 W strings on for 6 hours over 40 nights use 115.2 kWh.
Does the calculator include the price of the lights?
No. It covers the electricity only. LED sets usually cost more to buy but last much longer, and the DOE report notes manufacturers project up to 20 holiday seasons.
How old is the wattage data?
The DOE per-lamp figures come from a 2003 report that cites 2002 data, so today's LED sets can differ. That is why the watts are editable.
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Update history
- 2026-10-09 Launched: Christmas lights electricity cost calculator comparing LED and incandescent strings with Department of Energy wattages.