Space Heater
What size extension cord for a Space Heater?
A space heater draws about 12.5 amps (1500W) at 120V. To carry that safely you need at least 12 AWG copper, and even then only for short runs, up to roughly 25 ft before voltage drop and heat become a problem. Thinner cord (the common 16 AWG household type) can overheat under this load and is a fire risk.
Cord gauge by length for a space heater
The longer the cord, the thicker it must be to keep voltage drop under 3% at 12.5A. Minimum recommended copper gauge by run length:
| Cord length | Minimum gauge | Notes |
|---|---|---|
| 25 ft | 12 AWG | Minimum safe gauge |
| 50 ft | 12 AWG | Minimum safe gauge |
| 100 ft | 10 AWG | Upsized for the longer run |
| 150 ft | 8 AWG | Upsized for the longer run |
Safety note
Never use a standard 16 AWG extension cord with a space heater. Use 12 AWG minimum, keep as short as possible. NEC recommends direct outlet connection.
Why gauge matters
A smaller AWG number means thicker copper and lower resistance. Undersized cord drops voltage (making motors and heating elements work harder) and turns the lost energy into heat in the cord itself. At 12.5A, a too-thin or coiled cord can get hot enough to melt insulation. Always uncoil cords fully during use, and never chain two cords together for a high-draw space heater.
Frequently asked questions
What gauge extension cord for a space heater?
Use at least 12 AWG copper for a space heater (12.5A). For runs longer than 25 ft, step up to the next thicker gauge to hold voltage drop under 3%.
How long can the extension cord be?
At 12 AWG, keep it to about 25 ft for a space heater. Beyond that, use a thicker cord: see the gauge-by-length table above.
Can I use a regular 16 AWG cord?
No. A standard 16 AWG household cord is not rated for the 12.5A a space heater draws and can overheat. Use 12 AWG or thicker, and ideally plug the space heater directly into a wall outlet.
Disclaimer: For reference only. Consult a licensed professional.