How Much Does It Cost to Run Christmas Lights? (Washington Power Bill Math)

This is the question people ask right before they say yes, and the answer surprises them. With LED bulbs, a fully lit roofline costs about as much to run for the entire season as a couple of coffees.

The formula

Watts, times hours, divided by one thousand, times your rate per kilowatt-hour. Puget Sound Energy residential rates run in the neighborhood of twelve cents per kilowatt-hour, so we will use that.

A real example: 300 bulbs, full season

Say your roofline takes about 300 C9 bulbs, running six hours a night for the 45 nights between Thanksgiving and early January.

Same look from the street. Ten times the operating cost. That gap is the entire argument for commercial-grade LED, and it is before you count the bulbs incandescent strings burn through in a wet Northwest December.

Three ways to spend less than that

• Put it on a timer. Six hours instead of dusk-to-dawn cuts run time roughly in half. A photocell timer costs a few dollars and pays for itself the first week.
• Light what people see. A well-designed front elevation reads better from the street than lights wrapped around the back of the house that nobody looks at.
• Stop mixing old strings in. One run of incandescent can cost more than everything else combined.

Where the real cost actually is

Electricity is the small number. The expensive parts of DIY holiday lighting are the ladder time, the strings that fail after two seasons, and the emergency trip to the hardware store on December 18. That is the math worth running before you decide to do it yourself.