Testing extension cords to find out which is best

Originally published at: Testing extension cords to find out which is best | Boing Boing


@garethb2 I just wanted to say, thanks for including the bottom line in your summary. I wish all front-pagers did that instead of requiring us to watch the video.


Pro tip:
Cheap extension cords with high voltage drops can double as space heaters, and electric space heaters convert electricity into heat at 100% efficiency! (But once the cord’s insulation starts combusting it may be a good idea to get a new one.)


As usual, an impressively conducted set of tests. Most of those brands I’ve never seen before, at least, not in extension cords. I was surprised to see Husky, which had a close association with The Home Depot, but seems to have been largely phased out in favor of the HDX brand.

I wonder how many of these properties are regulated by UL. For example, testing the voltage drop revealed very little variation from brand to brand for cords that used the same gauge wire. I bet the jacket material tells you more about the how the jacket will wear than the brands themselves.

Other tests I would have liked to see include actual length versus advertised length and how the material holds up under UV light.


Voltage drop is a function of load, (amperage) length, and cross-sectional area of the wire (gauge), and the “amp” rating on the packaging is very much related to allowable voltage drop for that size conductor.

Before clicking through to the video, I’m going to guess that the “SJ” type cables have less abrasion resistance and tensile strength than the “S” type, and that the most flexible are the SOOW/SJOOW followed by SEOOW/SJEOOW with STOW & SJTOW as the worst. The markings required by UL are quite informative to the initiated.

The always-delightful Technology Connections did a video on extension cords some time ago.

It’s intriguing that apparently one of the reasons there aren’t more problems is that an appropriate level of fear and caution has been successfully instilled in the populace.


Husky is owned by HD. Any back and forth between Husky and HDX brands is the result of Home Depot marketing and badging decisions.

I use an extension cord to plug in the charger for my PHEV. You know, like you’re not supposed to do, but that is the only way it will reach my parking spot. The number one reason is because even if the cord is properly rated, the wall socket (or more precisely the fit between the plug and the socket) may overheat when carrying a constant 12 Amps. The charger itself has a temp sensor in the plug and will shut down if it gets too hot. It can’t detect that if plugged into an extension cord.

Long story short, the hefty over-gauged $60 cord on a reel, complete with multiple outlets, surge protection, a circuit breaker, etc… melted down at the plug and destroyed the wall socket. Replaced it with a new GFCI, returned the overpriced cord, and got a $20 one from Horror Freight. I’ve been using it so long the red has faded to pink from sun but it doesn’t overheat.

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