4 Things to Know About Outdoor Extension Cord Ratings

Look for STW, not SJTW The “J” in SJTW means junior—thinner insulation that’s fine for light indoor use but not built for weather, mud, or being stepped on. STW has no “J,” meaning a thicker, more durable jacket.

S stands for Service cord This means the cord is flexible and designed for portable use, not fixed wiring inside walls.

T stands for Thermoplastic The PVC jacket is standard for most extension cords, but the thickness varies between SJTW and STW.

W stands for Weather-resistant Both SJTW and STW are weather-resistant, but only STW has the abrasion resistance and cold-weather durability for heavy outdoor use like running a miter saw in wet grass or leaving a cord out all season. The price difference is usually a few bucks—not worth saving if the cord splits after one winter.