How Much Do Christmas Lights Cost to Run?

The formula

Every string of lights has a wattage on its tag or box. Add up the watts, multiply by hours of use and divide by 1,000 to get kilowatt-hours (kWh). Multiply by your electricity rate.

cost per night = total watts × hours per night ÷ 1,000 × price per kWh

season cost = cost per night × number of nights

How many watts do holiday lights use?

Read the tag on each string; wattage varies a lot by bulb type, count and brand. As a rough guide:

Strings sold as a set often list the wattage for the whole set, not for each strand, so read the label carefully. Older strings may have lost their tags; a plug-in energy meter will measure them exactly in a minute or two.

Inflatable yard decorations have fans and lights and often draw more than a few strings of LEDs. Check their labels too.

Worked example: incandescent vs. LED

A house display has 10 strings, lit 6 hours a night for a 40-night season, at an example rate of $0.15 per kWh.

The LED display uses one eighth of the energy. A big display multiplies both figures, so the savings grow with the number of strings. Put in your own wattage, hours and rate in the electricity cost calculator; enter the total watts, or the watts per string and the number of strings.

Hours matter as much as bulbs

The same single string over a 40-night season, at $0.15 per kWh:

Multiply by the number of strings for your whole display.

Will the lights trip a breaker?

A typical North American 15-amp circuit at 120 volts can supply 1,800 W, and for loads that stay on for hours it is good practice to stay under 80 percent of that, or 1,440 W. That is about 36 strings of 40 W incandescent lights, counting everything else already on the circuit. LED displays rarely come close. If breakers trip, spread the display across more circuits rather than adding more cords to one outlet.

Finding your electricity rate

Look at your bill for the price per kWh. If it splits charges into energy and delivery, add the per-kWh parts together. If you are on time-of-use pricing, evening hours are often the most expensive, which is exactly when lights are on. In that case use the evening rate.

Ways to cut the cost

• Use a timer. Lights that turn off at bedtime instead of running all night use a fraction of the energy. Six hours instead of twelve halves the cost.
• Switch to LED as old strings wear out. They also run cool, which reduces fire risk on trees and wreaths.
• Turn them off when you are away. A smart plug lets you control them from your phone.
• Do not count the tree twice. Indoor tree lights add the same way as outdoor strings; include them in your total.

Safety for holiday lights

• Use only lights and extension cords rated for outdoor use outside, and plug them into outlets with ground-fault (GFCI) protection.
• Check the tag for the maximum number of strings that can be connected end to end, and do not exceed it.
• Inspect strings for cracked sockets, bare wire or loose connections, and throw away damaged sets.
• Keep a live tree watered; a dry tree catches fire easily. Turn lights off before bed or when you go out.
• Use a fiberglass ladder for outdoor electrical work, never metal, and keep yourself, the ladder and the lights at least 10 ft (3 m) from overhead power lines. Have someone steady the ladder when hanging lights on the roofline.

Frequently asked questions