If the weather stays this beautiful we'll definitely put up our outdoor lights this coming weekend.We have a huge pinon tree in the front that I have always dreamed of loading with lights for a festive Holiday display.
But just how many strands can I add together? How do I calculate the number of lights I can use? I get that question a lot from our clients these days. It's actually pretty simple. First you need to go to your breaker box and find out which circuit you are going to use. Plug one strand into the outlet you want to use and check out each switch on the breaker box until you have located which one lights up your light string. There is a number on the switch that tells you the amps load for the circuit. That's the number you are looking for. Usually it is 15 or 20.
Also check if it only lights up your Holiday lights or if anything else is connected to it. Just so you know how many watts are already in use. If you want to use a lot of lights for your Holiday decorations, you'd want only those lights to be on the circuit, so you can more easily calculate the load. Then again, if you are using only LED light strings you'll see below that the load can be minimal.
Multiply the amount of amps you read on the switch by 120, which is the common household voltage. 15 x 120 = 1800, that's the amount of watt you can use on that circuit. It is a good idea to deduct 20% , since you don't want to load the circuit to it's max. A power surge could then cause the breakers to trip easily and your entire display would go dark. With 1440W you have a lot to work with, especially with the incredibly energy saving LEDs. I am looking at some from American Lighting that offer 250 lights using only 5W. I could truly go wild with my outdoor lights if I wanted to.
There is, however one more thing to look out for: the gauge of the wire for the light strings. You might have noticed that commercial string lights use much thicker wire for their strings. This is important if you want to do really long runs, especially if you use incandescent lamps. It might be tempting just to hook one small cheap light string onto the next and keep going until you are all around the house and got the job done. Not a good idea. UL safety recommendations advise that only 216 watts of string lights be used on one circuit, and remember it says circuit, not outlet. But luckily most string lights you buy come with a built-in fuse that is designed to blow if you overload the string, so you don't damage your Christmas lights or worse. With LED light strings you don't have this issue, since they use so little energy. Yet another reason to love them. LED light strings are of course a lot more expensive to purchase and you might still have your incandescent light strings from years past. So you might be doing the switch slowly over some years. Nothing wrong with that. You just need to add up the numbers and for the incandescent light strings you'll need more outlets, since you can't string as many of them together.
If you have 300 ft. of roof line you want to cover on your home and your string lights have the usual 12 inch spacing between each bulb, you of course need 300 bulbs. Using incandescent bulbs it will take 2,100 watts to power your lights. Since you can only add about 4 - 5 strings together you'll need multiple outlets. In contrast LED bulbs will only require 26+ watts and you can practically string all the lights you desire together using just one outlet.