Can I mix incandescent and LED Christmas lights?

March 13, 2014

This is a tricky question because the answer depends on what type of lights your are looking at.

String Lights

(with series wiring – ie. mini lights, craft lights and pre-wired LED string lights)

For string lights, it’s important to stick with one family of lights in series because LED and incandescent lights pull vastly different amounts of current.  (If you think of electricity as a river, current is a measure of how much water is flowing.)  LED’s only need a little current and if you run them in series with a much higher resistance traditional string of mini lights then you run the risk of damaging your lights or worse, starting a fire.

It’s a good idea to only run string lights in the same family together in one run.  Only LED’s in a run or only traditional lights in a run.  When it comes to traditional lights, it’s best not to run lights of various number of bulbs together in series but stick to running lights with similar characteristics in single runs.

Socket Wire with Separate Bulbs

(With Parallel electrical connection)

Traditional socket wire with heavy duty wiring is generally wired in parallel.  All of the stringer cord that we carry is wired in parallel.  This means that the electrical current is delivered to each bulb on the circuit in only the quantity that it needs.  (Constant voltage, variable current for those of you who want this in techno-speak.)

Your can see examples of these types of stringers at C7 cords and C9 cords.

Because these cords are wired in parallel, you actually can run traditional incandescent or filament bulbs in the same run as LED bulbs.  You could alternate painted blue or opaque bulbs with LED bulbs for different textures in your lighting.

Aside from style considerations, also keep in mind that even though you might use a large number of LED bulbs, the longest run of stringer wire that you can safely operated cannot exceed the maximum length rating of the cord itself.  LED bulbs don’t carry much current but if 18 AWG wire is run too long, it can act like it’s own fuse and you can blow your breaker or worse start an electrical fire.

For 18 AWG wire, we don’t suggest any run longer than 250 feet.

Ultimately, if you are running custom lengths of cords together in series, consult with a master electrician to confirm your wiring is safe and within the specifications of your materials.

If you choose to go all incandescent keep in mind that C7 and C9 bulbs range in wattage from 5 to 10 watts.  We suggest that you don’t exceed 1000 watts per breaker.  Again, consult with a local master electrician.

Well, I hope that this answers your questions.  If you have any technical questions, please contact an electrician or if your question is related to a product, please contact us at Contact Page.

6 thoughts on “Can I mix incandescent and LED Christmas lights?”

  1. I’m having some real frustrations with ~80 ft of C9 incandescent bulbs. Replaced fuses first, but that burnt out. Noticed that 2 of the lines had 10 A fuses while the other 2 had 5 A fuses, so I swapped out the 5 A for 10A fuse stringers. Worked, but then the whole line went out again. Am I putting too much current through the lights? Would swapping in some led C9s drop the current draw to a manageable level for the fuses? Ive confirmed voltage is being delivered to the line, so the problem has to be with the light setup as opposed to the circuit breaker…

    1. The manufacturer chose the 5-amp plug based on the electrical specifications of your cord. It sounds like you have overloaded your cords or they have become damaged over time. I would reboot with a new cord instead of putting your investment in LED bulbs at risk.

  2. I have several “older” strings of lights/decorations
    and now have a few new LED decorations ALL
    plugged into one electric strip. Some of the older incandescent decorations went “dark” the second I flipped the strip on. Why???

    1. Wow – that is really unusual. Did you try plugging them in by themselves?

      It sounds as though too many of them were plugged in end-to-end and you might be looking at an issue of blowing the fuses. Or the power strip might need replacement.

      It’s hard to say but these might be a couple of first things to consider.

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