When shopping for an outdoor extension cord, most people look at length, color, or gauge—but few pay attention to the mysterious letters printed on the jacket.
SJTOW, SJTW, STOW… they may look like random codes, but these small combinations of letters tell you everything about a cord’s durability, safety, and best use.
So before you grab the nearest orange cord for your tools or Christmas lights, let’s decode what these letters actually mean—and how to pick the right one for your needs.
Why Cord Letters Matter More Than You Think
Every outdoor extension cord carries a story written in code. Those letters—SJTOW, SJTW, STOW—aren’t there for decoration; they’re your safety manual in shorthand.
Each letter describes something specific: how tough the jacket is, whether it resists oil or water, and whether it can survive a snowy backyard or a hot garage.
Choosing the right one isn’t about being an electrician—it’s about protecting your tools, your lights, and your home.In short: decoding these letters means powering up safely, efficiently, and confidently.
Understanding the Cord Letter System
The lettering system comes from the UL (Underwriters Laboratories) and National Electrical Code (NEC) standards.
Each letter in a cord’s name describes its construction, insulation material, voltage rating, and environmental resistance.
Think of it like a car’s model code—each letter adds a feature that determines how it performs.
Here’s what the most common letters stand for:
| Letter | Meaning | What It Describes |
| S | Service | Standard 600V-rated cord used for portable tools or appliances |
| J | Junior | 300V rating — lighter duty than full 600V “S” cords |
| T | Thermoplastic | PVC insulation; flexible and durable |
| E | Elastomer | Rubber-like flexible jacket for extreme cold or heat |
| O | Oil-resistant | Resists oil, grease, and chemicals — ideal for garages or workshops |
| W | Weather- and Water-resistant | Safe for outdoor use, resists sunlight, rain, and snow |
The “O” and “W” letters are your best friends outdoors — they’re what make your cord survive rain, snow, and oily driveways.
SJTOW vs SJTW vs STOW: What’s the Difference?
Once you know the letters, you can instantly tell the difference between cords just by reading the label.
Here’s how the most common outdoor extension cord types compare:
| Cord Type | Voltage | Jacket Material | Resistance | Best Use |
| SJTW | 300V | Thermoplastic (PVC) | Weather-resistant | General outdoor household use — Christmas lights, garden tools, light-duty appliances |
| SJTOW | 300V | Thermoplastic (Oil-resistant) | Weather + Oil-resistant | Garage, workshop, or anywhere oil and water may mix |
| STOW | 600V | Heavy-duty Thermoplastic | Oil + Weather-resistant | Industrial, construction, or high-power outdoor equipment |
● SJTW cords → SJTOW cable features an oil-resistant and weather-resistant PVC jacket, making it ideal for outdoor hard-service applications. Built with 18–10 AWG conductors and PVC insulation, this 300V AC cord offers reliable performance in environments exposed to oil, moisture, and harsh weather.
● SJTOW cords → SJTW cable comes with a weather-resistant PVC jacket designed for outdoor use. Using 18–10 AWG conductors and rated for 300V AC, this hard-service cord delivers steady performance in wet, cold, and general outdoor conditions, but is not oil-resistant.
● STOW cords → STOW cable is a heavy-duty, oil-resistant and weather-resistant cord rated for 600V AC. With PVC insulation and 18–6 AWG conductors, it supports tougher applications and is widely used in industrial tools, construction sites, and rugged outdoor environments.
If you’re plugging in a leaf blower, go with SJTW.
For power tools in your garage, choose SJTOW.
Running equipment on a job site? STOW is your guy.
This DEWENWILS ground stake timer and outdoor extension cord combination delivers waterproof SJTW durability and UL Listed safety—ideal for powering outdoor Christmas tree lights through the winter season.
How to Choose the Right Extension Cord for Your Job
When selecting a cord, match its strength to the task—not all cords are created equal.
● For holiday lights or yard décor: SJTW cords are flexible, safe, and weather-rated for outdoor use.
● For garage or workshop tools: Choose SJTOW cords with oil-resistant jackets.
● For high-amperage equipment or generators: STOW cords offer industrial-grade protection and 600V strength.
Pro Tip: Always check the AWG (wire gauge)—the smaller the number, the thicker the wire and the more power it can handle safely.
Example:
● 16 AWG = light duty (Christmas lights, small tools)
● 14 AWG = medium duty (lawn mowers, snow blowers)
● 12 AWG = heavy duty (power saws, generators)
And here is a tip for more information on extension cord safety: Top 10 Extension Cord Safety Mistakes Every Homeowner Must Avoid
Durability, Flexibility, and Safety in Every Season
Outdoor power cords endure everything from blazing summers to frozen winters, so materials matter.
● Here’s how to keep your cord working longer:Avoid sharp bends — always coil loosely to prevent internal wire fatigue.
● Store indoors when not in use — UV rays can degrade the jacket over time.
● Choose a flexible jacket if you live in cold climates; SJTOW cords remain pliable even below freezing.
● Check certification marks (UL, ETL) to ensure your cord meets U.S. safety standards.
DEWENWILS SJTW outdoor extension cords combine flexibility, weather resistance, and safety for year-round reliability.
For a deep dive into seasonal risks and solutions, don’t miss our companion article: Why Outdoor Extension Cords Matter This Winter.
Decode the Letters, Power Up Safely
Now that you know what those cryptic letters mean, choosing a safe extension cord becomes easy.
Every letter—S, J, T, O, W—adds a layer of protection between your power source and your project.Whether you’re hanging Christmas lights, trimming the hedges, or running heavy-duty tools, decoding your cord means fewer hazards, longer lifespan, and peace of mind every time you plug in.
So next time you see SJTOW or STOW, you’ll know: that’s not random—it’s reassurance.
Frequently Asked Questions About SJTOW, SJTW, and STOW Cords
What’s the Difference Between SJTOW and SJTW Extension Cords?
SJTOW cords are both oil- and weather-resistant, while SJTW cords are weather-resistant only.
If you’re using your cord in a garage, workshop, or cold outdoor area, go with SJTOW—it stays flexible in freezing temperatures and resists grease or oil. For most outdoor lighting and garden tools, SJTW cords provide reliable weather protection.
Can SJTW Extension Cords Be Used for Outdoor Christmas Lights?
Yes — SJTW outdoor extension cords are rated for weather and moisture resistance, making them perfect for powering Christmas lights, inflatables, and garden decorations.
Always check for UL or ETL certification and ensure connections are elevated or covered to prevent water seepage in snow or rain.
Which Type of Extension Cord Is Best for Cold Weather?
SJTOW cords perform best in freezing environments. Their flexible thermoplastic jacket resists cracking in sub-zero temperatures, unlike standard indoor cords.
For year-round reliability, choose DEWENWILS 16/3C SJTOW or SJTW cords, which remain durable and pliable from summer heat to winter frost.
Is STOW the Same as SJTW?
Not quite. STOW cords are heavier-duty, 600V-rated cables designed for industrial or construction use. SJTW cords, rated at 300V, are more flexible and suited for home and outdoor appliances.
If you’re powering high-amperage tools or generators, choose STOW; for yard or holiday use, SJTW is safer and easier to handle.
How Do I Know Which Outdoor Extension Cord to Buy?
Check three key details:
Letter code (SJTOW / SJTW / STOW) → tells you where it can be used.
Wire gauge (AWG) → thicker wire = more power.
Certification mark (UL / ETL) → ensures safety and compliance.
For most homeowners, a 14 AWG SJTW cord offers the perfect mix of power, flexibility, and safety for outdoor setups.
