The question behind the December bill
Every January the same posts appear: "my electricity bill jumped $60 - was it the Christmas lights?" Usually the honest answer is partly. A modern LED display is genuinely cheap to run - a whole typical house display costs less per season than one takeaway pizza. But an old-school display is a different animal: one string of 25 big C9 bulbs draws 175 watts, twenty-five times a modern LED string, and a house still running a dozen of them is heating the night air with real money. This calculator exists because the difference is invisible until the bill arrives - and because the other calculators ask for your total wattage, a number nobody knows. You know how many strings you own. That is enough.
How much electricity do Christmas lights use? The wattage table
| Type of light | Watts | Season cost at 6 hrs/night, 35 nights, $0.17/kWh |
|---|---|---|
| LED string, 100 lights | about 7 W | about $0.25 |
| Incandescent mini string, 100 lights | about 40 W | about $1.43 |
| Incandescent C9 string, 25 big bulbs | 175 W (7 W per bulb) | about $6.25 |
| LED C9 string, 25 bulbs | about 15 W | about $0.54 |
| Yard inflatable | about 150 W | about $5.36 (at 6 hrs - many run far longer) |
| LED projector | about 7 W | about $0.25 |
The maths behind every figure on this page is one line: watts × hours a night × nights ÷ 1,000 × your rate. The calculator just does it for a whole display at once - and runs the LED version of your display alongside, so you can see what the old strings are really costing you.
What a whole display costs: three real houses
| Display | In LED | With old bulbs |
|---|---|---|
| Modest - a few strings and one inflatable | about $7 a season | about $15 a season |
| Typical suburban house - roofline, tree, inflatables | about $10-17 a season | about $25-45 a season |
| The house everyone drives to see | about $20-50 a season | $100-300+ a season |
Two things push a display from the left column toward the right: old bulbs, and hours. The second is sneakier - an inflatable left running 24 hours a day costs four times what the same inflatable costs on a 6-hour timer, and it is usually the single biggest item on a real December bill, ahead of every string of lights combined.
Three ways to cut the cost without dimming the display
Put everything on a timer. Dropping from 8 hours a night to 5 cuts the running cost by about 37% - and nobody is admiring your roofline at 2 a.m. anyway. Outdoor timers cost a few dollars and pay for themselves in the first season. Replace the worst offenders first. You do not need to re-buy the whole display: the C9 strings and old mini strings are nearly all of the wattage. Swap those two and a mostly-old display drops to nearly LED money. Mind the inflatable. If it only inflates when people can see it - dusk to bedtime - it stops being the most expensive decoration you own.
Planning the rest of the season? The Christmas Budget Calculator plans the whole holiday spend, and the Coffee for a Crowd Calculator covers the drinks for the party itself.
Frequently asked questions
How much does it cost to run Christmas lights for a season?
A typical modern LED display - several strings plus an inflatable, 6 hours a night for about 35 nights - costs roughly $7-17 for the whole season at average US electricity rates. The same display in old incandescent bulbs runs about $15-45, and a large old-bulb display can pass $100-300.
Do Christmas lights use a lot of electricity?
LED lights do not: a 100-light LED string draws about 7 watts, less than a phone charger, and costs about 25 cents a season to run. Old incandescent lights are the exception - a mini string draws about 40 watts and a single C9 bulb 7 watts, so a big old display can draw as much as a small heater.
How much cheaper are LED Christmas lights to run than incandescent?
About 85-90% cheaper for the same brightness. String for string, 7 watts against 40 - and against old C9 bulbs the gap is wider still. On a whole-house display that is the difference between about $15 and about $45 a season, and the LEDs last for many more seasons too.
How many watts is a string of Christmas lights?
A 100-light LED string is about 7 watts; a 100-light incandescent mini string about 40 watts; a 25-bulb incandescent C9 string is 175 watts because each big bulb alone is about 7 watts. Your box prints the exact figure for your set - this calculator has a custom-watts row if you want to use it.
Does putting Christmas lights on a timer really save money?
Yes - the saving is exactly proportional to the hours. Running 5 hours a night instead of 8 cuts the cost by about 37%. Timers also end the 2 a.m. forgotten-display problem, which on a big old-bulb display is where a noticeable slice of the December bill hides.
Why did my December electricity bill jump if LED lights are so cheap?
Usually it is not the light strings. The common culprits are an inflatable running 12-24 hours a day (its fan never stops), space heaters and heated blankets in guest rooms, more cooking and laundry with visitors, and - if you still have them - old C9 or mini incandescent strings. This calculator lets you test each suspect separately.