How much do Christmas lights cost to run?

January 2007 - When asked, my wife refers to me as an “interesting” person as apposed to odd, nerdy or weird. And so when presented with an idea that gives most people a loss of words or a feeling of social unrest (e.g. my three year light bulb experiment in the garage which I share with all house visitors), she usually shakes it off as just part of my “interesting” character. That has recently came to an end though, as on the morning of December 2nd I informed her we’re conducting a month long study on how much our Christmas lights cost to operate.

Every fall I drag myself out to the garage and spend a good portion of the morning and afternoon untangling a series of Christmas lights that have mysteriously found themselves in a rat’s nest. It’s simply amazing how Christmas lights can spend all year tangling themselves without me even knowing. After a bit of emotional counseling and a frank discussion with my inner self, I spread them out and dangle them haphazardly from my shingles using duck tape.

My light collection is made up of thirty to forty feet of “icicle” lights consisting of around 1330 bulbs. As a side note, these lights are the ones where if one simple bulb burns out, the rest of the string finds itself in the dark. Ironically, these are the ones I always end of hanging on the tall dangerous part of the roof. We then have 120 smaller lights that are used to string around a bush or two. In all, we have around 1450 candescent light bulbs hanging from various spots.

The study was conducted as so. On select nights when the temperature was going to be consistent for two consecutive nights, I shut my Christmas lights off early and took a meter reading at 10PM and 7AM the following morning (night one). The following night I did the exact same thing with the exception of leaving my Christmas lights on all night (night two). Assuming all other variables are consistent (e.g. furnace fan run rate or the number of times my wife turns on the light for a bathroom run), the difference between night one and night two should give us the amount of kilowatt hours it takes to run our Christmas lights. This figure divided by the number of hours (i.e. 9 hours) gives us the kilowatt hours needed to run these crafty little buggers per hour.

And so the results are in. Night one consistently shows we use three kilowatt hours of electricity to run the house. This is primarily due to our furnace fan, the running fan in the bedroom (i.e. the noise maker), and my wife’s annoying alarm clock, which by the way goes off every nine minutes between 6 and 7AM. Night two consistently shows we use seven kilowatt hours (the arithmetic mean is actually 7.33) to run the house with the Christmas lights flaring all night. For those of you who are math deficient (like me), the difference is four kilowatt hours. Meaning it takes four kilowatt hours of electricity to run our 1450 Christmas light bulbs for nine hours or close to .444 kilowatt hours per hour. Looking at my last electric bill we pay $.0725 per kilowatt hour meaning our total cost for an hour of Christmas lights is a little over three cents.

So what does this mean? Honestly it really means nothing other than if you hang Christmas lights and leave them on four hours every day in December, you can expect to pay three to four dollars extra on your electric bill. Even a fiscal conservative like me can handle the expense for a little seasonal excitement in the neighborhood. Happy holidays!