Professionals use commercial-grade Christmas lights. You can't find them at big-box retailers, so you'll have to go to a specialty supplier like Christmas Lights Etc or Christmas Designers.

LED options, especially commercial-grade, may be more expensive than traditional incandescent lights One of the most important things to look for in Christmas lights is how easily you can replace ...

the Brizled Christmas String Lights are our favorite overall. Available in three different lengths, the LED bulbs—which have 11 lighting modes—are waterproof, dimmable and affordable.