Real World Christmas Lights Scenario
The example house on the right needs 265 ft. of lights. The homeowner could go with LED or incandescent lights. Either option would look great, but what the homeowner may not realize is that the electrical needs for each are vastly different and require different plans.
If the homeowner chooses LED lights they could string all 265 ft. together, end to end and plug them all into a single plug...but the LEDs are more expensive. If the homeowner chooses less expensive incandescent bulbs they'd have to run six separate strings that each use separate outlet plugs. And, it's highly likely the homeowner would have to make sure they were using two different house circuits to handle the capacity.
Either option would look fantastic but the LED option is 38 watts whereas the incandescent option is 1,925 watts. Both options can be easily planned for, but the incandescent option requires more understanding of what your home can handle as well as what your strings can handle.
Christmas Lights Wattage and Amps
Understanding Christmas light wattage and amp current helps to ensure a reliable and safe Christmas lights display. Wattage has an impact in every area of Christmas lights from planning to installation. Once you find out your bulb wattage and understand how amperage affects your project, shopping for Christmas lights and customizing light displays becomes a lot easier.
Wattage and amps should be considered in two key areas:
Understanding the Max Capacity of String Lights
Some LED Christmas lights require so little electricity that you can plug over 80 sets together end to end without a problem. A comparable set of incandescent Christmas lights may only allow you to connect four end to end. Why? Because light strings have a maximum wattage capacity, which is why many string lights come with a little fuse just in case you connect too many together at once. The fuse is designed to blow so you don't overload and damage your Christmas lights. When you select your string lights it is important to consider how many can safely be connected together based on your project needs. But...you also need to consider where you plug your lights into as well.
The Maximum Watt Capacity of Your Plug Circuit
A typical household circuit can include several plug outlets, internal lighting fixtures or built-in appliances all on the same circuit. This means that whenever you plug your Christmas lights into the wall they are sharing that circuit's capacity with anything else that may also be drawing power. If very few things are on the circuit you have more wattage capacity. However, if your circuit already has a number of items drawing power from it, you may begin "tripping your breakers" in the fuse box. This happens when your wattage exceeds the amp capacity of the circuit.
Most household circuits are 15 or 20 amps
It is recommended that all circuits never exceed 80% of their max wattage capacity
15 amp circuits support 1,800 watts (80% capacity is 1,440 max watts)
20 amp circuits support 2,400 watts (80% capacity is 1,920 max watts)
How Many Watts Do My Christmas Lights Use?
Watts is a measurement of the amount of energy used. Wattage is typically provided per bulb or string and is listed on the bulb or near the UL tags on a string. If wattage is not listed on the stringer or bulb, wattage meters are available for around $10 to calculate its electric draw. Incandescent lights use more electricity than LED lights but either light type is good. You just need to plan for it accordingly.
Real Life Mini Light Wattage Scenario
It's fairly common for people to wrap their porch railing, columns or front windows with mini lights. Inside the home it is also common to wrap trees, hearths, mantles or stair railing with mini lights as well. The side chart highlights a common scenario where you might need about 10-15 strings. Light counts can vary by string so to do a fair comparison, you'll need to compare bulbs to bulbs. If you use 1,000 incandescent mini lights the total watts used is about 408, whereas using the same amount of LEDs, would only be 69 watts. The incandescent string lights can only have 5 sets connected end-to-end, which mean you would need to use two plug outlets. The LED lights can have up to 43 connected end-to-end while using only one plug outlet. Either light type will create a great display, but the incandescent mini lights will require a little more planning to make sure you don't overload the capacity of your strings. While this example only uses a small amount of string lights, it's not uncommon for people to use 40+ sets of string lights to decorate their bushes, trees or landscaped areas. With incandescent mini lights, this would require planning for 8 separate plug outlets. LEDs would still only need 1. Again, either option can look great, but incandescent requires more careful electric planning.
Real Life C9 & C7 String Light Wattage Scenario
C9 and C7 Christmas bulbs are very popular choices for roof lines, but planning between LED and incandescent can be extremely different. If you need 300 ft. of C9 lights to cover all the roof lines of your home with traditional 12 inch spacing between each bulb, you're looking at 300 bulbs. Incandescent bulbs will look incredible, but will take 2,100 watts to power. LED bulbs will also look impressive, but will only require 29 watts. The wattage difference is extreme!
Both LED and incandescent lights in this example have 25 bulbs per string, which is very common. With incandescent, only 2 strings can be connected end-to-end, which means you'll need 6 different plug outlets. With the LED option, up to 87 strings can be connected together, which means the 12 you need for this project can be connected end-to-end and then plugged into a single outlet.
Tip: Because the incandescent option requires 2,100 watts, which is more than most household circuits can handle, you will need to separate your light runs onto different household circuits. This is not difficult, but it requires you to know which plugs in your house to use...otherwise you'll be running to the circuit breaker box often to flip blown fuses. The other planning consideration with this scenario is that you can only run 2 incandescent strings end-to-end. This means you have a maximum of 50 ft. to work with before you have to switch to a different plug outlet with a new run of your lights. Often times this method involves the use of extension cords or carefully planning various rooms in your house that have access to roof lines. There are easier planning options that include going with commercial grade, heavier gauge wiring so you can include more bulbs in larger runs, but this is also more expensive.
Why even consider incandescent? Granted, they're more difficult to properly plan for, but incandescent Christmas lights tend to be less expensive than LEDs, so if initial cost is a critical planning aspect for your project, incandescent may be a good option. While LED lights save money long-term, they often cost more up front. If you only use your Christmas lights sparingly a few weeks out of the year, you may not see the energy savings for several seasons which makes incandescent bulbs a popular choice. Also, many people like the look of incandescent bulbs because of the unique light halo they produce. They have that nostalgic quality that LED bulbs do not. Both bulb options can look fantastic, but incandescent options like this simply require more planning to do properly.
How Does Light Wattage Relate to Amp Capacity?
Watts measure a unit of energy. Amps measure a unit of current. Amp capacity refers to the total amps that can be supported.
Amp capacity in string lights determines how many bulbs can be used in a single length of wire. This typically applies when stringers and C7 or C9 bulbs are sold separately and lighting is customizable. All stringers and spools at Christmas Lights, Etc list amp capacity in the product specifications. Staying within 80% of the amp capacity of a wire ensures Christmas lights stay lit throughout the season.
Amp capacity in a household circuit determines how many total watts can be plugged into a full circuit, regardless of how many outlets the circuit contains. Outlets connected to a single circuit share that circuits Amp capacity, so be sure to also take into account other items running of the same circuit, such as lamps, electronics or appliances. Staying within 80% of the amp capacity of a circuit ensures the breakers don't trip.
When using Christmas light strings where the bulbs are hard wired into the socket or where the bulbs are screwed into the socket, total amps is usually listed in the UL tag near total watts.
When total amps is not provided, first calculate total watts, and then calculate for amps.
Calculate amps by dividing total wattage by 120 volts (US household outlets carry 120 volts)
How Many Christmas Lights Can I String Together?
Christmas Lights, Etc follows UL Standards regarding max strings connected, or how many light strings can be plugged together into a single outlet opening. UL listed lights state a maximum of 210 watts can be connected when using 22 gauge wire, and a maximum of 420 watts can be connected when using 20 gauge wiring. Below is a quick reference chart listing popular Christmas light strings, wattage examples and maximum strings connected. Note that both LED and incandescent lights can be used for just about any application but that incandescent lights require far more power and therefore require more planning to make sure the string capacity and the circuit capacity are adequate.
Christmas Lights Power Consumption
How Much Power Can I Save with LED Christmas Lights?
LED Christmas lights wattage is significantly less than incandescent lights and the bulbs always stay cool to the touch. LED lights save money both on the power bill and as an investment: with strings rated at 50,000+ hours average life versus 3,000 for incandescent lights, LEDs can be reused for years. To read more about LEDs and their benefits, check out the LED Christmas Lights Guide.
Can I Save Power by Using a Timer?
Yes, timers help in saving power by scheduling exactly how many hours to run Christmas lights. When selecting a timer, be sure to check for Amp capacity. Note that if you choose a 15 Amp timer and use it with a 15 Amp circuit, that circuit can still only support 15 Amps total - the timer does not add Amp capacity to a circuit, it supports Amp capacity of the lights that are plugged into it.