How to crunch the numbers on your own Christmas display
Only the likes of Ebenezer Scrooge would judge a lighting display by how much electricity it uses. That’s why this story – which compares LED (light-emitting diode) to incandescent outdoor decorative lights – focuses instead on how technology can help us realize our full festive potential.
The calculations below may seem like the stuff of penny-pinching, but they’re only meant to, well, enlighten us about how easy and inexpensive it can be to turn our homes into beacons of holiday cheer.
“The new LEDs use about one-fifth of the power of the old incandescent lights, so there’s a major savings,” says NAIT Electrician instructor Matt Charlton (Electrician ’00).
Just how substantial are those savings and what do they mean to your set up? Let us count the watts.
Power in numbers
Each circuit, or breaker, in your home can support up to 1,440 watts of power. With LEDs, get ready to rival the constellations if your outdoor socket is on its own breaker (which in newer homes often is) and therefore solely devoted to your display.
To find out how many strings you can use on one plug, says Charlton, “you can just add them up if the boxes say how many watts they are.” If they don’t, and don’t say how many strings can be connected, allow for five watts per string (larger “C9” bulbs may rate higher). That can mean – we’ll wait while you get your sunglasses – 20,160 lights.
If you want to crunch your own numbers, this is the way:
- 1,440 watts / 5 watts per string = 288 strings
- If each of those 288 strings has 70 lights, offers Charlton as example, that’s 20,160 lights, or about enough to keep the neighbourhood up at night.
In the old days, when five- to seven-watt incandescent bulbs ruled the winter night, you’d trip your breaker with about 288 to 205 lights, respectively, or just a few strings.
Power for pennies
Comparatively, you’d also spend much more to run those incandescents. At today’s electricity prices (in kilowatt hours), running a maxed-out light display for, say, five hours a night for the month of December would cost $16.74.
Again, for the math enthusiasts:
- 288 lights x five watts per light = 1,440 watts or 1.44 kilowatts
- 1.44 kilowatts x five hours x 31 days = 223.2 kilowatt hours
- 223.2 kilowatt hours x $0.075 cents/kilowatt hours (approx. 2014 rate) = $16.74
Running the same number of LED lights, or about three five-watt strings, costs $0.23 – for the entire month. If you run them for four months a year, what you save would pay for the lights (assuming $20 to $25 per box) in a couple of seasons.
Or, put more simply, “The old lights use a ton of electricity,” says Charlton.
Powerful decorating tips
To make your display even more efficient, Charlton recommends using both a photocell and a timer. With the photocell, lights follow the decreasing sunlight until winter solstice. “When daylight goes away your lights turn on.” The timer turns them off whenever you choose.
To avoid disappointment and make sure they turn on in the first place, use strings that are wired so they won’t turn off if just one goes out. LEDs last up to 50,000 hours but they’re still susceptible to damage.
Regardless of the savings, Charlton points out, LEDs will inevitably disappoint some decorators.
“The old lights look better,” he says. This is a matter of measurement, he says, not taste. Incandescent lights approximate daylight in a way LEDs don’t, creating a colourful glow rather than a pinpoint of light. “When people say they look at bit dull,” says Charlton of the latter, “it’s true.”
That’s not to say he’s living like some ghost of Christmas past. Charlton is content to light up his outdoor display of candles, deer and other symbols of the season with LEDs knowing a brighter future awaits. With each Christmas, he says, “the technology is getting better.”