Window AC Unit
What size extension cord for a Window AC Unit?
A window ac unit draws about 10 amps (1200W) at 120V. To carry that safely you need at least 12 AWG copper, and even then only for short runs, up to roughly 15 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 window ac unit
The longer the cord, the thicker it must be to keep voltage drop under 3% at 10A. 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 | 12 AWG | Minimum safe gauge |
| 150 ft | 10 AWG | Upsized for the longer run |
Safety note
Window AC units should ideally plug directly into an outlet. If an extension cord is necessary, use 12 AWG max 15 ft.
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 10A, 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 window ac unit.
Frequently asked questions
What gauge extension cord for a window ac unit?
Use at least 12 AWG copper for a window ac unit (10A). For runs longer than 15 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 15 ft for a window ac unit. 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 10A a window ac unit draws and can overheat. Use 12 AWG or thicker, and ideally plug the window ac unit directly into a wall outlet.
Disclaimer: For reference only. Consult a licensed professional.