It’s that time of year again when it gets dark at 4:00 pm and the only thing keeping us sane are the wonderful holiday lights lighting up the neighborhood and classic Christmas movies. One of my favorites is National Lampoon’s Christmas Vacation. Famously, Clark Griswold covers his home in lights and we see his energy meter spinning out of control.
Watching this movie got me thinking: how much energy do those lights consume, and how many solar panels would it take to cover that demand?
Let’s dive in and look at the numbers!
Table of Contents
The Lights
According to the product description page from Ace Hardware, a 100-count strand of these lights requires 40.8 Watts to run. If those were run for one hour, the lights would consume 40.8 watt hours. Homeowners are charged for energy in terms of kilowatt/hours (kWh), which is 1000 watt hours (Wh).
Today, it’s more common to use LED lights because they are significantly more efficient. The same 100 count strand of lights in LED would only use about 6 Watts. Had Clark been able to use LED’s his power bill and solar panel need would be a lot less.
Total Consumption
The movie isn’t specific about how long the lights are on for so we’ll have to make some assumptions. Let’s assume the lights are turned on once it gets dark (4 pm) and go off late in the evening once everyone goes to bed (11 pm).
40.8 W * 250 Strands= 10,200 W or 10.2 kW
10.2 kW * 7 Hour/day= 71.4 kWh/day
It’s implied by the movie timeline that Clark puts up his lights on December 14th, but because it isn’t explicitly stated, let’s keep it even and say the lights are up from December 1st-31st. That’d mean the total consumption of the Griswold house is:
71.4 kWh/day * 31 Days = 2,213 kWh
That’s 2,213 kWh of energy from the Christmas lights alone, without anything else running in the house! No wonder the town needed to switch over to auxiliary power.
Panel Production
So how many solar panels would be needed to run those lights? Well, it’s good to note that solar panel production takes a serious drop in the winter due to snow and the lack of sunlight.
To estimate panel production we can use PV Watts from the National Renewable Energy Lab (NREL). Christmas Vacation is supposed to be based in the Chicago Suburbs, so I set the PV Watts location to Chicago, IL.
In real solar system builds a solar consultant would look at a home’s annual usage needs and try to cover as much of a home’s yearly energy as possible. For this calculation, we’ll look at how many panels it would take to produce 2,213 kWh of energy in just December.
What Would It Take?
After running several PV watt simulations, the chart below shows that Clark Griswold would need to install a 36 kW DC solar array on his home to completely cover his Christmas lights usage. With a 400W panel, the Griswolds would have to install 90 panels on their home.
If you’ve got aspirations of exterior illumination like Clark Griswold, make sure to add Solar Insure’s SI-30 Solar to your project so you can keep spreading holiday cheer for the long term.
Happy Holidays from all of us here at Solar Insure!
