How many string lights can be on one outlet depends on a number of varying factors, including the total wattage of your circuit, the type of lights, the energy needs of the lights, and cord specifications. It’s better to play it safe here to protect your circuit, so figure out the max wattage of your circuit, compare that to the lights, and move on from there. Generally speaking, LED string lights require less energy than incandescent bulbs, translating to a higher number of lights per circuit. 

To hang Christmas lights on a ceiling without using nails or traditional hooks, you have several damage-free options. Adhesive hooks and clips are a popular choice. For smaller projects, you can use pushpins, tacks, or adhesive putty. Specially designed transparent tape that can hold weight without damaging paint is also effective. For a more creative approach, consider stringing the lights over a curtain rod near the ceiling. If you have a drop ceiling, look for clips and hooks designed to attach to the metal framing. Note that staples can also be used, but may leave small holes.

The easiest way to hang Christmas lights on your roof is to attach them to your gutters, but there are plenty of user-friendly methods to try. You can use light clips to easily hook Christmas lights to your shingles, eaves, gutters, or soffit. However, using a telescoping pole is a surefire way to ensure your safety while hanging Christmas lights because it doesn’t require using a ladder or climbing onto the roof.

Aside from a professional light installation company, there are a few other pros who may be able to help you hang Christmas lights. Along with specialty holiday decorators, a handyperson near you can also hang Christmas lights (and can fix that pesky drippy sink while they’re at it). Either way, not all of these pros will offer the service, so be sure to call ahead and get multiple quotes before you hire.