LED against incandescent

A 100-light incandescent mini set draws around 40 watts. The LED equivalent draws around 5. That is not a marginal efficiency gain, it is a different order of magnitude, and it is why the two are worth treating separately in every calculation.

The practical consequence is that chain limits stop mattering. Five incandescent mini sets fill a 210 watt run; you would need forty LED sets to do the same. Most people never approach the limit with LEDs, which is why so much of the old advice about counting sets feels irrelevant now.

Take a display of twenty 100-light sets running six hours a night for thirty nights. Incandescent: 800 watts, 144 kWh, which is a genuinely noticeable amount on a bill. LED: 100 watts, 18 kWh.

At typical residential rates that is the difference between a meaningful line item and a rounding error. It is also the difference between needing a second circuit and not.

Color. Incandescent light has a continuous spectrum and a warmth that cheap LEDs do not reproduce — early LED sets in particular had a blue-white cast that people disliked for good reason. Good warm-white LEDs have largely closed this gap, but the cheapest ones have not.

There is also the flicker question: inexpensive LED sets often run direct from rectified line voltage with minimal smoothing, which produces visible flicker in peripheral vision and in photographs. If your phone shows banding when filming a set, that is what you are seeing.

Do not chain LED and incandescent sets together on the same run. The chain limit is set by the cord in the first set, and putting a heavy incandescent load behind a light LED set is exactly the case that overheats a cord.

The calculator handles mixed displays: add each type as its own row and it works out the chain limit for whichever type is tightest.