UL Standards and LED Christmas Lights

June 19, 2016

UL or Underwriter’s Laboratory is an independent product certification organization, which creates standards and tests electrical and other products, for many U.S. and foreign manufacturers. UL has become the industry standard for safety certification of electronic devices in the U.S. This certification is not a legal requirement, but most reputable companies who manufacture or sell electronic devices, seek the UL certification.

In order to obtain UL approval for a product, the product must meet the standards created by UL, for that specific type or class of electronic device. UL’s standards also proscribe the conditions under which the certified product, or prospective certified product, may be used. UL has a standard for decorative lighting strings or what is commonly called Christmas lights. The use standards UL proscribes for Christmas lights are the same, regardless of whether the light string utilizes an incandescent or LED light source. The original certification, known as UL 588, limited the end-to-end connection of string lights to just three sets – But, this standard has been revised multiple times to reflect the great differences between LED and incandescent lighting technology.

The old UL standard was really a source of confusion for consumers and vendors of LED Christmas lighting products, because the newer LED product drew between 80-90% less power than the older incandescent lights, but UL still only approved the end-to-end connection of 3 light sets. Which just goes to show that the original UL standard was developed specifically for incandescent Christmas lights (and their much higher power draw), and not the more efficient LED options that are now available.

In recent years, UL has finally acknowledge that the standard should be different for LED Christmas lights, and in 2010 changes were made to allow each light strings connect-ability to be rated by Watts and Amps. The new standard states:

CAUTION: This lighting string is rated ___ Watts (__Amps), do not overload. Connect other lighting strings or decorative outfits end-to-end up to a maximum of 210 Watts (1.75 amps) total.


  • EX: 50ct set of incandescent mini lights will generally be about 25’ long and will draw 20.4 watts. With this new UL rating, you can connect up to 10 sets end-to-end = 250’ of lights


  • Our 50ct or 70ct LEDs will be 23’-25’ long and will draw 4.8 watts. With this new UL rating, you can connect up to 43 sets end-to-end = 989’-1075’ of lights.

As you can see, this is a great improvement in connect-ability (for both the incandescent and LED product) over the 3 end-to-end they used to allow, but the difference it makes for LED installs is much superior.

In 2014, UL updated this again, to increase the end-to-end connection up to a maximum of 216 Watts (1.80 Amps).


  • EX: This change in rating does not affect the connect-ability of the 50ct incandescent mini lights we referenced above, as you can still only connect 10 sets end-to-end.


  • It does affect the LED sets thou, as you can now connect up to 45 sets of our 50ct or 70ct LEDs end-to-end = 1035’-1125’ of lights

As you can see, this change in rating makes a huge difference when decorating with LED products. You are no longer limited to only connecting 3 sets end-to-end, have to run multiple extension cords to each item you want to decorate, or have to take a refresher course each fall on amps/watts and how to calculate them – Just light and enjoy!

For more advantages on why you should switch to LED products, please see our article LED Holiday Lights vs. Incandescent Holiday Lights: Time To Convert?