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What does the season of lights cost?
Enter your strings by bulb type, the nightly hours, and your electric rate — the season's kWh, cost, and LED-swap savings come out below.
FREE CALCULATOR · MONEY
Christmas Lights Cost Calculator
One LED string costs pennies a season — a box of old incandescent bulbs costs dollars. Count your strings, set your hours, and price the season's glow — then see what swapping to LED saves.
How it works: watts = (incandescent strings × watts per string) + (LED strings × watts per string). Energy = watts × hours × nights ÷ 1,000 = kWh. Season cost = kWh × your rate. The all-LED comparison prices the same string count entirely at your LED wattage; swap savings = your cost − all-LED cost, and the payback divides the price of new LED strings by the per-season savings.
How the Christmas lights math works
Your electric bill charges for energy — kilowatt-hours — not for lights. A kilowatt-hour is 1,000 watts running for one hour. So the whole calculation is one chain: how many watts all your strings draw together, times how many hours they are on each night, times how many nights, converted to kWh and priced at your rate.
The formula
watts = (incandescent strings × W each) + (LED strings × W each) · kWh = watts × hours × nights ÷ 1,000 · season cost = kWh × $/kWh
Worked example: 20 strings, mixed
Ten incandescent strings at 40W each (400W) plus ten LED strings at 5W each (50W) = 450W total. On 6 hours a night for 31 nights: 450 × 6 × 31 ÷ 1,000 = 83.7 kWh. At $0.17/kWh that is $14.23 for the season — about $0.46 a night.
Per string per season, the math is even starker: one incandescent string costs 40 × 6 × 31 ÷ 1,000 × $0.17 = $1.26; one LED string costs $0.16. Swapping those ten incandescent strings saves about $11.02 a season — at $9 a replacement string, the new LEDs pay for themselves in about 8 seasons on energy alone, and they last 10+ seasons.
The bars above price the same comparison for your own numbers — your display against its all-LED twin.
Where this comes in handy
- Answering the December-bill question: price the display before the bill arrives — lights are usually the smallest suspect, but now you know exactly how small.
- Deciding whether to swap old strings: the payback line tells you how many seasons the new LEDs need to earn their price back.
- Sizing a timer's savings: drop the hours field to your timer's window and watch the season cost fall — the classic 5 PM–11 PM window costs half of an all-night burn.
- Checking circuit load: the watts total tells you whether the display is anywhere near a timer or outlet's rating before you plug it in.
- Comparing bulb types at the store: the watts-per-string fields are the whole ballgame — a 40W string and a 4W string look identical from the curb.
For the full strategy — the timer question, the swap decision, and why your December bill still jumps even with LEDs — see the guide How much do Christmas lights cost to run?. For the rest of the holiday budget, use the holiday budget calculator.
Christmas lights cost — frequently asked questions
How much does one string of Christmas lights cost to run?
At 6 hours a night for 31 nights at $0.17/kWh, a 100-bulb incandescent string (~40W) costs about $1.26 for the season; an equivalent LED string (~5W) costs about $0.16. Multiply by your string count — the bulb type is the whole story.
Do LED Christmas lights really use 90% less electricity?
Yes — roughly. A 100-bulb incandescent string draws about 40 watts; a comparable LED string draws about 4–5 watts, which is an 88–90% drop. The price gap between an all-incandescent and an all-LED display is about ten to one.
Do timers save money on Christmas lights?
They save runtime, and runtime is money. Cutting a display from all-night (say 14 hours) to a 5 PM–11 PM timer window cuts the season cost by more than half. A cheap mechanical timer pays for itself the first December.
Is it worth replacing working incandescent strings with LED?
For the energy alone, the payback is slow: swapping ten 40W strings for $9 LED strings saves about $11 a season, so the new strings pay for themselves in roughly 8 seasons. The real argument is longevity and safety — LEDs last 10+ seasons and run cool — and the swap pays back much faster on big displays.
Why did my December electric bill jump if the lights are so cheap?
Because lights are a small slice of winter demand. Heating (or a heat pump working harder in the cold), shorter days meaning more indoor lighting, extra cooking, and guests with hot showers usually move the bill far more than the lights do. Price the display in the calculator, then look at heating and hot water for the rest.
How many watts can I safely plug into one timer or outlet?
Check the labels: a standard US household circuit is 15 amps (about 1,800W), and most plug-in timers are rated well under that. LED displays almost never get close; big incandescent displays can. Outdoor lights also belong on a GFCI-protected, outdoor-rated timer — never an indoor-only timer outside.
Do twinkle or chase settings use more electricity?
Slightly more on the fancy settings, sometimes less. Twinkling and chasing add controller draw but keep many bulbs off at any instant; some LED strings use noticeably less on "slow glow" modes than on steady-on. The difference is small next to the bulb-type choice.
Do inflatable yard decorations cost more to run than lights?
Usually yes. An inflatable's fan draws roughly 60–150 watts continuously — more than ten LED strings combined. Two or three inflatables can cost more to run than the entire light display.