LED vs incandescent Christmas lights, with the arithmetic shown
Watts, amps, kilowatt-hours and dollars for the same display, with every assumption stated so you can substitute your own.
By Sawyer V. · Published
Everyone knows LED costs less to run. Almost nobody publishes the number, and the number is the interesting part — because it turns out the running cost is the smaller half of the argument. The bigger half is how many strings you can put on one circuit.
Here is the whole thing worked out, with the assumptions printed so you can change them.
Wreath & Watt earns a commission on qualifying purchases made through the Amazon links on this page. It costs you nothing and it does not change the order of the picks — here is exactly how we are funded.
Our assumptions, stated
The numbers
| Incandescent | LED | |
|---|---|---|
| Watts per string | 40 W | 5 W |
| Total watts | 800 W | 100 W |
| Amps at 120 V | 6.67 A | 0.83 A |
| Kilowatt-hours per season | 216 kWh | 27 kWh |
| Cost at 17 cents/kWh | $36.72 | $4.59 |
| Strings on one 15 A circuit | 36 | 288 |
Every figure in the table is computed from the assumptions above. Nothing here is a quoted price or a measured result.
Source: Watts = volts x amps at 120 V. The 80 percent ceiling is the standard continuous-load convention for a load running three hours or more. Per-string wattages are the figures published for those bulb types; the tag on your own string is what actually governs.
The arithmetic
- Incandescent: 20 strings x 40 W = 800 W
- 800 W x 6 h x 45 nights = 216,000 Wh = 216 kWh
- 216 kWh x $0.17 = $36.72 per season
- LED: 20 strings x 5 W = 100 W
- 100 W x 6 h x 45 nights = 27,000 Wh = 27 kWh
- 27 kWh x $0.17 = $4.59 per season
About $32 of difference per season on a 20-string display.
The running cost is not the real argument
Thirty-two dollars a season is real money but it is not decisive, and anyone telling you LED pays for itself immediately is selling something. Over five seasons the energy saving on this display is around $160, which will cover the conversion for a modest display and will not for a large one.
The decisive number is the last row of the table. On a single 15 A circuit you can run 36 incandescent strings or 288 LED strings. If your display has ever tripped a breaker, or if you have ever run a second cord across the lawn to a different outlet, that is the row that matters. LED does not save you money so much as it removes the ceiling.
What you actually lose with LED
Two things, and both are real:
- Color rendering. An incandescent filament produces a continuous warm spectrum. LEDs approximate it, and cheaper warm-white LEDs land slightly green or slightly pink in a way that shows most against snow. Better sets are close enough that most people would not pick them out; the difference has not gone away.
- Serviceability, sometimes. Many LED mini strings are sealed. A C9 LED set with screw-in bulbs keeps the advantage; a sealed LED mini string does not, and neither does an incandescent one.
There is also a genuine argument for keeping incandescent on one small feature — a single wreath, a doorway — where the warmth is at close range and the load is trivial. Nothing about the arithmetic forbids that.
Can you mix them?
On the same circuit, yes, and the calculator handles it: add a row for each type. On the same run, no — do not connect LED and incandescent sets end to end. Beyond the connection limits published on each set, the visible difference in color temperature along one continuous line looks like a fault.
Our picks for this
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 | No imageNorthlight LED mini lights, 100 count, 33 ft, green wire100 LEDs, 4 in spacing, 33 ft lighted length | Trees, shrubs and wrapping — the workhorse string | 6.3/ 10 | Check price #ad · Disclosure |
| 2 | No imageIncandescent mini lights, 100 count, 20 ft, green wire, UL listed120 V incandescent — roughly 40 W per 100-count stringSkip this | People who genuinely want the old warm glow | 5.3/ 10 | Check price #ad · Disclosure |
Scores are our own weighting of published manufacturer specifications, explained in full on how we research. They are not test results. We have not tested these products.
The picks, in detail
#1 — Trees, shrubs and wrapping — the workhorse string
Northlight LED mini lights, 100 count, 33 ft, green wire
100 LEDs, 4 in spacing, 33 ft lighted length
6.3
/ 10
The default mini string. Buy the count you need for the tree, not the count that was on sale.
Published specifications
- Count
- 100 LED mini bulbs
- Spacing
- 4 in
- Lighted length
- 33 ft
- Wire
- Green
- Rated wattage per string
- Not published by the manufacturer
Our scoring
- Build
- 7 / 10
- Weather tolerance
- 7 / 10
- Serviceability
- 5 / 10
- Published specs
- 6 / 10
Good
- 4-inch spacing over 33 feet is the density most tree-wrapping guidance assumes
- Green wire disappears into evergreen far better than white
- LED draw means you can run many strings on one circuit — see our amp guide
Watch out
- Wattage is not printed on the listing, so you have to read the tag on the string itself
Specs from the Amazon listing (ASIN B073WJBKPX), retrieved 2026-09-04.
#2 — skip this
Incandescent mini lights, 100 count, 20 ft, green wire, UL listed
120 V incandescent — roughly 40 W per 100-count string
5.3
/ 10
Skip this unless the incandescent glow is specifically what you are buying. On a 15 A circuit it costs you three quarters of your strings.
Published specifications
- Count
- 100 incandescent mini bulbs
- Lighted length
- 20 ft
- Voltage
- 120 V, UL certified
- Twinkle
- No twinkle function
- Typical draw
- About 40 W / 0.33 A per string (industry convention for a 100-count mini set)
Our scoring
- Build
- 5 / 10
- Weather tolerance
- 5 / 10
- Serviceability
- 4 / 10
- Published specs
- 7 / 10
Good
- The color rendering LEDs still approximate rather than match
- Cheap enough to treat as consumable
Watch out
- Draws roughly ten times the watts of an equivalent LED string, which caps a 15 A circuit at about 36 strings
- Bulb failures cascade in series sections
Count, length and voltage from the Amazon listing (ASIN B08BJW25WK), retrieved 2026-09-04. The 40 W figure is the standard published draw for a 100-count incandescent mini string and is the same figure used in our load arithmetic.
Questions
›How much does it cost to run Christmas lights for a season?
For 20 strings of 100-count mini lights at 6 hours a night for 45 nights: about $37 for incandescent and about $5 for LED, at 17 cents per kilowatt-hour. Change the rate to your own and the arithmetic on this page still holds.
›Are LED Christmas lights brighter than incandescent?
Usually brighter and always cooler in tone, which is a different thing. The practical difference people notice is color rendering rather than raw output: incandescent produces a continuous warm spectrum that LEDs approximate.
›Can I mix LED and incandescent Christmas lights?
On the same circuit, yes. On the same connected run, no — the connection limits differ and the color mismatch along one continuous line reads as a fault.
Sources
- Northlight LED mini listing (ASIN B073WJBKPX) — 100 count, 4 in spacing, 33 ft
- Incandescent mini listing (ASIN B08BJW25WK) — 100 count, 20 ft, 120 V, UL certified
- Per-string wattages — 40 W incandescent and 5 W LED per 100-count mini string; the tag on the set governs
- Electricity rate assumption — 17 cents per kilowatt-hour, stated as an assumption and substitutable
We have not tested these products. Every figure above comes from a published manufacturer specification or from arithmetic shown on this page, and anything a maker does not publish is printed as unavailable rather than estimated. How that works, and what we will not claim, is set out on how we research.