For sixty years the answer to "how many lights" was "as many as your wiring allows." That era is over. The real question now is which bulb you put on the string, because one number does all the deciding: the watts per bulb. Get that wrong and everything downstream follows you into trouble. Get it right and the rest of the purchase is noise.

I have pulled incandescent strings off customer eaves for a decade, and the wire felt hot to the hand even at rest. That is not a detail. It is the whole argument in one sentence, and it is the one most buyers never make until after the season that almost went bad.

The Wattage Gap: 5 to 6 Watts vs Under 1

A C7 incandescent bulb draws between 5 and 6 watts, and a C9 runs 11 to 15 watts. A 100-count C7 strand is therefore a 500 to 600 watt load; a C9 strand is closer to 1,100 watts before it touches a single extension cord. That is a wall of heat sitting on your roofline at 2am on a cold night.

The LED version of the same string, same bulb count, same wire, draws between 40 and 90 watts. An 8.5W LED C7 and a 0.8W LED C7 look identical to a passer-by at 20 meters. The draw does not. On a 100-count strand you are cutting the load by 85 to 90 percent. That is the number the Energy Star program has used for a decade, and it holds on real strings, not lab fixtures.

For a storefront running twelve strands overnight, that is the difference between a 7kW load and a 700W load. The first trips the meter on a cold December night when the HVAC kicks in. The second does not even register on the breaker.

The Heat Number You Never See on the Box

Incandescent filaments run 180 to 200 degrees Celsius. Quality LED strings stay under 50 at the bulb, and a good driver keeps the whole run under 40. That is the difference between a surface you can touch and a surface that will not touch back. Dry pine garland, aged burlap, a decades-old roof membrane: none of those have a margin against a 180-degree surface pressed against them for six hours a night.

The failure I see most often is not a visible fire. It is a char mark. A single amber spot on the burlap where a C7 sat too long. The customer never reports it; they just order fewer bulbs the next year, the string gets darker, and the whole install quietly reads as "the old guy" to people walking past. A 45-degree LED bulb never produces that mark. That is the whole fix in one line: not a better string, a cooler one.

The Cost Math and the One Spec That Matters

Buy the LED string for two to three times the price of the incandescent version. Run it four months a year, eight hours a day, at 35 euro cents per kWh. The incandescent strand costs roughly 12 to 15 euros a year per 100-count run; the LED strand costs between 1 and 2 euros. Payback lands inside the first season. After that it is pure margin, for you if you are stocking it.

The spec to check is the driver, not the bulb. A 0.8W C7 on a 100-count string is an 80W load, so the driver should be rated for 150W or more. Anything less is a coin flip on shelf life. This is the number the spec sheets hide under "power supply" and "transformer." Same thing. Check it. I have seen two strings with identical LED counts and identical wire, different driver part numbers: one lives to year five, one does not survive the second December. That is the whole industry in one line, and it is why the cheap string and the good string look exactly the same on the shelf.

If you are stocking for more than one season, buy a string with an outdoor transformer rated for the climate you are actually in. An IP67 driver in a UK winter is a different product than an IP44 one in the same winter. And buy from a supplier who stands behind the driver, not just the bulb. The bulb is the easy part; the driver is where the warranty actually lives. When I stock a string I check the driver rating and the return policy before I check the lumen count, because those are the numbers that decide whether the string is still there in March.

Our christmas string lights range covers the full C7 and C9 LED set. For the warm-white run, the warm white christmas lights line is what I stock for storefronts. For eave and outdoor work, the outdoor christmas lights set is rated for the climate.

Frequently Asked Questions

Q: How many watts does a 100-bulb incandescent C7 christmas string lights strand draw?
A: A C7 incandescent draws 5 to 6 watts, so a 100-count strand is a 500 to 600 watt load. The LED version of the same string draws 40 to 90 watts, an 85 to 90 percent cut.

Q: Are led christmas lights cooler to the touch than incandescent?
A: Yes, by a wide margin. An incandescent C7 runs 180 to 200 degrees. A quality led christmas lights string stays under 50 at the bulb. That gap is the difference between a surface that chars burlap and one that does not.

Q: How long do led christmas lights last compared to incandescent?
A: An incandescent filament is rated at 1,000 hours. A quality LED is rated at 25,000 to 50,000 hours, though the driver usually fails before the LED. That is why the driver rating, not the bulb count, is the spec to check before you buy.