Safety
The Wrong Extension Cord Gauge Gets Hot Enough to Start a Fire
Running a space heater on a light-duty extension cord is one of the most common preventable causes of house fires in cold months.
Wire gauge determines resistance, and resistance under load generates heat. A cord rated for 13 amps asked to carry the 15 amps a space heater draws will run measurably hotter than one properly rated, especially over long runs where resistance adds up.
Coiling a cord that's still under load compounds the problem: the tightly wound loops trap heat against each other instead of letting it radiate away, which is why a coiled cord can get noticeably warmer than the same cord run flat.
| Amp draw | Minimum cord gauge (25 ft) |
|---|---|
| 7 amps | 16 AWG |
| 10 amps | 14 AWG |
| 15 amps | 12 AWG |
| 20 amps | 10 AWG |
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