I have to tell you something about the extension cord.
You probably have three of them right now. One behind the TV. One in the garage that’s been there since before you moved in. One in a tangled heap in a box somewhere. I do, anyway.
They seem simple. Wire with a plug on one end and a socket on the other. What’s to know?
Plenty, as it turns out.
Before Extension Cords, Your Appliances Hung From the Ceiling
Here’s something I didn’t know until Tuesday. Before 1904, if you wanted to plug in a toaster or an iron, you had to unscrew a light bulb from the ceiling socket and screw the appliance into the bulb socket instead. Your toaster dangled from the ceiling by its cord. If it fell, it ripped out of the socket and you had a short circuit and a burnt breakfast.
This was apparently considered normal for about 20 years.
In 1904, two things happened. An engineer named S.W. Atherton invented the extension cord — basically a wire with a plug on one end and a socket on the other, so you could bring power down from the ceiling to where you actually needed it. Same year, Harvey Hubbell II patented the detachable plug. The two-pronged plug you use today is still Hubbell’s design. He founded Hubbell Incorporated, which is still in business in Connecticut. (SPARK Museum, Connecticut History)
Gloria Swanson Apparently Invented One
That Gloria Swanson. Norma Desmond from Sunset Boulevard. “I’m ready for my close-up” Gloria Swanson.
She co-founded a company called Multiprises in 1938 that developed one of the first extension cords. Her company also helped Jewish inventors flee Nazi Germany. The woman famous for playing a faded movie star clinging to the past was literally in the business of extending reach. (Vice)
I have to say, that’s a better Hollywood ending than anything in the movie.
Why Some Are Thicker Than Others
This is where I spent 20 minutes in the electrical aisle.
Wire thickness is measured by American Wire Gauge (AWG), and the numbers are backwards. Lower number = thicker wire. 10 AWG is a big thick boy. 16 AWG is skinny lamp cord.
The rule of thumb: for a 50-foot run, you want 16 AWG for a lamp or phone charger, 14 AWG for medium stuff, and 12 AWG for tools or appliances. If you’re running 100 feet to a shed, go 12 AWG or thicker. The longer the cord, the more voltage drops through the wire — your tool gets less power and has to work harder, which heats everything up. (Wikipedia - AWG)
So if you’ve ever used a long skinny extension cord on a saw and wondered why it sounded sad, that’s why. The cord was eating your power before it reached the tool.
The Coiled Cord Wants to Burn Your House Down
This is my favorite fact.
An extension cord coiled up on a reel while in use generates heat that can’t escape. The inner coils get trapped against each other, the heat builds up, the insulation melts, and you get a fire. The National Electrical Code requires derating — a cord on a reel might only handle half its rated current.
The thing that makes it convenient to store is the thing that makes it dangerous to use. That feels like a metaphor for something, but I’m not sure what. (Electronics StackExchange)
Your Cord Probably Has Lead in It
Look at the tag on any extension cord you own. See the California Proposition 65 warning? “This product contains chemicals known to the State of California to cause cancer.” That’s the lead in the PVC insulation. The EU banned lead in electrical products years ago. The US hasn’t. So wash your hands after handling extension cords. I’m not making this up.
The Orange Cord Is Everywhere
The bright orange 12/3 SJTW extension cord is the universal symbol for “construction zone.” You see it in movies, TV shows, memes — it instantly tells you work is happening. The color was chosen for visibility so people wouldn’t trip. It became a cultural signifier by accident.
And yet, for all their ubiquity, extension cords are officially considered temporary wiring by the National Electrical Code. You’re not supposed to use them permanently. Walk into any American home and you’ll find extension cords that have been in place since the Obama administration. They’re the electrical equivalent of that box you haven’t unpacked since you moved in 2014.
The One Rule You Should Actually Follow
Don’t plug a space heater into an extension cord. Space heaters draw 12-15 amps continuously — right at the edge of what most cords can handle. The cord heats up, the insulation melts, fire starts. Every winter, fire departments warn about this. Every winter, people ignore it. Be the person who doesn’t.
Also, daisy-chaining (plugging extension cords into each other or into power strips) is explicitly prohibited by fire code. Each connection adds resistance. Just get a longer cord. (ESFI, NFPA)
I went to Home Depot for one cord and came back with a story about Gloria Swanson and a new fear of my garage extension cord. The internet is amazing.
Doing our best to stay plugged in,
TH and Co.
PS> The xkcd about an extension cord with prongs at both ends came out in January and it’s exactly as cursed as you’d think. (xkcd #3198)