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How to calculate the energy savings of LED Christmas lights

Revised May 4, 2015

We frequently help our customers analyze the cost savings that can be achieved by using LED lights, instead of incandescent lights. The calculations to determine the cost savings are not very complicated, but just make sure you have a calculator handy (Thankfully, our Smart Phones all have one!). Our Energy Scrooge Calculator provides some interesting information about the benefits of LED lights, but we've never written about how to calculate the exact savings one can expect, by replacing their old incandescent Christmas lights with LED lights. Here's the data you will need to perform this calculation:

1. Total # of bulbs

2. Wattage of the individual incandescent bulbs to be replaced

The wattage is usually provided on tags that are attached to the light sets (typically provides wattage for entire light set). Incandescent C7/C9 bulbs will usually have the wattage stamped on the base.

Check your specific product for tags or stamps – If your light sets do not still have the tags on them, or your bulbs are not stamped, you can use the general guidelines below:

C9s are generally about 7-10 watts per bulb, C7s are generally about 5-7 watts per bulb, and mini lights are usually around .5 watts per bulb

3. Amount of time bulbs will be illuminated – In Hours

4. The average cost of a kilowatt hour of electricity in your area. ($.12/kilowatt hour is the current national average)

Step 1: Calculate total watts of Incandescent Product

Multiply the total number of bulbs, by the wattage of each bulb – This equals the total watts of the display
If the tag on your product supplies total watts for the set, you will need to multiply that number, by the total number of sets used in the display.

Step 2: Convert Watts to Kilowatt Hours

Multiply the total watts of the display, by the time the bulbs will be illuminated (in hours), and then divide that by the 1000 – This will give you the total Kilowatt Hours of the display.
Watts × Hours Illuminated ÷ 1000 = Kilowatt Hours

Step 3: Determine cost of electricity

Multiply the total kilowatt hours the display will consume (as determined in step 2), by the cost of a kilowatt hour of electricity in your area.
What you pay per Kilowatt hour can be found on your electric bill, or you can contact your local electric supplier. You can also find information and statistics, on the average cost of electricity, by searching on-line.

Step 4: Calculate total watts of LED product

Repeat steps 1-3 with the LED product, you are going to be replacing the Incandescent Product with. (LED is generally easier to calculate per set, as opposed to per bulb, as you are not dealing with so many decimal points).

Just like Incandescent, the wattage is usually provided on tags that are attached to the light set, and the bulbs will usually have the wattage stamped on the base.

Check your specific product for tags or stamps – If your light sets do not still have the tags on them, or your bulbs are not stamped, you can use the general guidelines below:

The average LED string light (50-70 LEDs) will be about 4.8 watts, Specialty Strings (Net Lights & sets of 100+ lights) can be up to 8.5 watts, the average LED Replacement Bulb will be around 1 watt.

Step 5: Calculate the savings

Subtract the cost of operating the LED lights from the cost of operating the incandescent lights. This is the total cost savings you can expect by switching to LEDs.