Don't use extension cords as permanent wiring.

No. Even heavy-duty outdoor extension cords are not designed for permanent or semi-permanent installation. They’re temporary tools, not substitutes for proper wiring.

The rating “heavy-duty outdoor” just means it can handle weather and high draw for a while—like powering a saw on a job site or holiday lights for a season. But extension cords lack the physical protection, secure connections, and code-compliant insulation of permanent wiring. Over time, sun exposure, vibration, and moisture degrade them. A cord that sits under a deck or runs along a fence for months becomes a fire hazard, no matter how thick the jacket is.

If you need power somewhere permanently, run a dedicated circuit or install a weatherproof receptacle. That’s the right way. An extension cord tucked behind the shed “temporarily” for two years is how sheds burn down.

Don’t do it. Get an electrician or run a proper outlet. Future you will be glad you did.