How many strings of Christmas lights can you connect?
Divide the most watts you can connect end to end by one set’s watts and round down: a 72 watt set with a 216 watt limit allows 3 sets. For incandescent lights, CPSC’s advice caps a run at three sets, even where the set’s limit allows more.
Kind of lights
If you’re not sure, pick Incandescent. It adds CPSC’s three-set cap.
For different sets in one run, type each set’s rating as a sum, such as 72 + 24, and enter the smallest limit printed on any of them.
How many sets?
Up to 3 sets in all
3 sets × 72 W = 216 W, within the 216 W limit. One more set would make 288 W.
Within CPSC’s limit of three sets of incandescent lights in a row.
To connect different sets, add up all their watts and stay under the smallest limit printed on any of them.
Unplug the lights before you connect or disconnect a set.
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Read the tag on the set’s cord, near the plug, and its instruction sheet. Together they give both numbers.
Where to find the numbers
Look for the flag-type tag on the cord, within 6 inches of the plug. It gives the set’s rating in watts (W), or on some sets only in amps (A). The instruction sheet gives the limit, in words like these from a GE mini set: “Connect other lighting strings or decorative outfits end-to-end up to a maximum of 216 Watts (1.8 Amps) total.”
Limits differ from set to set. A GE mini set allows 216 watts in all, and a Holiday Living C9 set 432 watts. Use the number printed for your own set, never one from another set.
Why the limit matters
Under UL 588, the safety standard for light strings, how much can be connected depends on the size of the set’s wire. Past that point, the wire can overheat.
Light sets made to UL 588 have a fuse in or near the plug. GE’s instructions give too many sets connected end to end as the most common reason a fuse blows.
Don’t overload outlets, and turn holiday lights off when you go to bed or leave the house.
Common questions
My tag only lists amps. What do I use?
Multiply the amps by 120 to get watts, as the makers' instructions say: a set rated 0.6 amps uses 72 watts. Or pick amps in the calculator.
Does the limit include the first set?
Yes. Add up the watts of every set in the run, including the one plugged into the outlet, and keep the total at or under the limit.
How many LED light strings can you connect?
LED sets use fewer watts, so more of them fit under the same watt limit: GE's LED C6 set of 100 lights is rated 8 watts, with a 216 watt limit, so 27 sets fit. CPSC's three-set limit is for incandescent sets.
The set ratings, the limits and the amps-to-watts step come from the light makers’ own instruction sheets, the three-set limit and the UL 588 summary from the CPSC, and the bedtime advice from the CPSC and the NFPA. Checked against published data from CPSC, GE, Holiday Living, NFPA and Nicolas Holiday.
See all 7 sources
US Consumer Product Safety Commission, Holiday Safety education center: no more than three sets of incandescent lights strung together
US Consumer Product Safety Commission, staff briefing package on seasonal and decorative lighting products (2014): UL 588 wire size, fuse and connection limits
GE mini light set instructions, models 61515LO and 61516LO (Nicolas Holiday, 2025): set watts, end-to-end maximum, amps times 120, fuses, GFCI outlet outdoors
Holiday Living light set instructions: clear C9 set W11C0154 (432 W maximum) and 6.5 ft. pre-lit Seneca Pine tree W14L0441 (lights rated 24 W, 216 W maximum)
National Fire Protection Association, Winter Holiday Safety tip sheet (2025): number of light strands to connect, lights off at bedtime
US Consumer Product Safety Commission, “Do’s and Don’ts of Holiday Decorating” (2009): tested lights, damaged sets, lights off at bedtime
LED 100 C6 light set instructions, model 3LED-C6-100(0.067) (Nicolas Holiday Inc., 2014; support at geholidaylighting.com): rated 8.0 W
General guidance from manufacturer and standards data. Products vary, so check the label and the maker's instructions.