Corded electric tools are the most affordable of all the tool types, but it does mean you have to manage an extension cord. Beyond that, it’s essential that you buy a cord specifically designed for outdoor use, for safety reasons and to maximize the power you get.
Extension Cords Are Not Created Equal
Extension cords, or otherwise referred to as power cords or electrical cords, whatever you prefer to call them, are a useful accessory and can be used for almost every electrical device on the market, giving us mobility and freedom so we can use our tools, gadgets and devices far away from a power outlet.
But far too many people are misinformed when it comes to purchasing the correct cord for their power tools. A common myth for people who don’t use power tools professionally, or on a regular basis, is the idea that all extension cords are created equal. Nothing could be further from the truth.
Too often consumers buy the cheapest extension cord they can find. This is a big mistake! By understanding the characteristics of an electrical extension cord, you’ll be better placed to select the optimal one for your power tools, ensuring maximum energy efficiency, peak performance, and safer operation.
How to Tell if an Extension Cord is For Outdoor Use?
When shopping for an outdoor extension cord, you may notice a variety of letters printed on the cord’s insulation or packaging. These letters are part of the extension cord designation, which provides important information about the cord’s characteristics.
When choosing an extension cord for outdoor use, pay close attention to the presence of the letter “W” or the combination “W-A” in the designation. It means that the cord is rated for outdoor use and has been approved as weather- and water-resistant.
More Extension Cord Designations
Curious about what those other letters on your extension cord mean? Here are a few common cord designations based on Underwriters Laboratories (UL) and National Electrical Code (NEC) – Article 400: Flexible Cords and Fixture Wires.
- J or SJ – The letter “J” or letter combination “SJ” refers to a “junior service” cord. The term “junior” indicates that the cord has a 300-volt insulation rating, making it suitable for powering the majority of appliances, tools, and electronics.
- S – The letter “S” typically signifies a cord with a thicker, more robust insulation rated for 600 volts. It allows the cord to handle higher amperage and wattage requirements, making it suitable for powering heavy-duty tools and equipment.
- T – If it’s not the first letter, the letter “T” indicates that the cord’s outer jacket is made from thermoplastic material, which is lightweight and suitable for light-duty, consumer-grade portable cords.
- E – The letter “E” stands for thermoplastic elastomer (TPE), a flexible material that performs better in colder temperatures than thermoplastic. If the cord lacks “T” or “E” in its designation, it is made of thermoset, which is suitable for heavy-duty applications.
- O or OO – When a single “O” appears, it indicates that the outer jacket is oil-resistant. However, if the designation includes a double “O”, it means that both the outer jacket and the inner conductor insulation are oil-resistant.
Let’s put this in practice and look at some examples.
So, What Does SJTW Mean?
When you see the letters “SJTW” on the extension cord’s jacket or packaging, what does it mean? To crack the code 🙂 , let’s break it down letter by letter. The “SJ” refers to a 300V junior service cord. The “T” refers to a thermoplastic jacket. And the “W” means the cord is weather resistant.
Or, What is a SJOOW cord? And… SOOW?
If you come across the letters “SJOOW” you’re dealing with a 300V thermoset cable with an oil and weather resistant jacket and oil resistant insulation while the letters SOOW refer to the same cord but with a 600-volt insulation.
What about SEOW vs SJEOW?
A “SEOW” extension cord is a 600V TPE cord that is oil and weather resistant while a SJEOW cord is the same cord with a 300-volt insulation.
How to Tell if an Extension Cord is Certified?
To determine if an extension cord has been tested and certified by an independent testing agency, look for the agency’s logo or mark on the cord’s insulation, plug, or packaging. The most common reputable, independent testing agencies in North America are:
- Underwriters Laboratories (UL) – Extension cords tested and certified by Underwriters Laboratories will feature the UL logo, which features the letters “UL” inside a circle.
- Intertek (ETL) – Extension cords tested and certified by Intertek will feature the ETL logo, which consists of the letters “ETL” inside a circle.
- Canadian Standards Association (CSA) – Extension cords tested and certified by the CSA will display the CSA logo, which features the letters “CSA”.
What Gauge Extension Cord do You Need?
An extension cord’s gauge refers to the thickness of the wires inside an extension cord, which directly affects the amount of current (amps) it can safely and efficiently carry. The gauge of an extension cord is typically represented by a number and the letters “AWG” (American Wire Gauge).
Whoever came up with the gauge ratings made things confusing for the average consumer. The lower the gauge number, the thicker the conducting wires inside the extension cord and thus the greater the flow of electricity.
If you’ve ever had an extension cord that felt hot to the touch, it’s likely the cord’s wire gauge was not suitable (too high gauge – too thin wires) for the electrical current required by your tool. As the electricity struggled to flow through these thin, inadequate wires, it encountered resistance, causing the wires to heat up.
So, you’re better off with a slightly smaller gauge (thicker wires, greater electricity flow) than a slightly larger gauge (thinner wires, less electricity flow).
To select the right wire gauge for your extension cord, you’ll need to keep two key factors in mind: the amperage (or wattage) of your power tool and the length of the cord you need.
Amps, Volts and Watts, Oh My!
Amperage (amps), Voltage (volts), and Wattage (watts) provide important information about a cord’s electrical capabilities and help users select the appropriate cord for their needs.
- Amperage (A) – The amp rating for an extension cord refers to the number of amps it can safely transmit based on its length and gauge.
- Voltage (V) – Extension cords are designed to work with specific voltages. In North America, standard household outlets provide 120 volts, while some specialty outlets, such as those for large appliances, may provide 240 volts.
- Wattage (W) – Wattage is a measure of electrical power and is calculated by multiplying the voltage by the amperage (W = V × A).
To ensure that the cord is capable of supplying enough power without being overloaded, it is crucial to choose a cord with an amperage, voltage and wattage rating that is equal to or greater than the electrical requirements of the device or devices you plan to power. Not doing so can lead to several problems.
- Overheating – When an extension cord’s wires are too thin to handle the required amperage, the cord can overheat. This can cause the insulation to melt, potentially exposing the wires and creating a fire hazard.
- Voltage drop – Thin wires have higher electrical resistance, which can cause a voltage drop along the length of the cord. This means that your power tool may not receive the full voltage it needs to operate efficiently, leading to reduced performance or even damage to the tool.
- Tripping breakers or blowing fuses – If the amperage draw of your tool exceeds the capacity of the extension cord’s wires, it can cause your electrical system’s breakers to trip or fuses to blow, interrupting your work and potentially indicating a safety risk.
To find the amperage, voltage, and wattage ratings of your power tool, you can look in several places such as the label on your tool, the user’s manual, or the manufacturer’s website.
If the wattage is not listed, you can calculate it using the amperage and voltage ratings. Remember, the formula is: Wattage = Voltage x Amperage. For example, if your tool is rated at 6 amps and 120 volts, the wattage would be: 120V x 6A = 720W.
Sometimes the power requirements of some tools are listed in watts only, and not amps. Use this formula to calculate the amps: Amperage = Wattage / Voltage. For example, to calculate the amps of a 1200-watt power tool, you simply divide 1200W by 120V to get 10A.
Keep in mind that some tools may have different amperage ratings depending on the mode of operation. Always refer to the highest amperage rating to ensure safe operation under all conditions.
Manufacturers are always trying to push the performance of their tools, but they face a limitation when it comes to electric tools. The standard US 120V household outlets are typically connected to 15-amp circuits designed for general lighting and everyday use.
As a result, most electric power tools have a maximum amperage rating of 15 amps, which restricts their overall power output. That’s why electric power tools can never compete with their gas counterparts when it comes to sheer power.
Also, if you plan on powering multiple devices from one outdoor extension cord, you need to be aware of their combined amp draws to ensure that the combined total isn’t higher than the amp rating for the cord to prevent overload.
If you’re still unsure about the electrical ratings of your power tool, contact the manufacturer’s customer support for assistance. They should be able to provide you with the necessary information based on your tool’s model number.
Does Extension Cord Length Matter?
Yes, it does matter. To select the appropriate gauge, you must also consider the distance the cord needs to cover as it directly affects its ability to deliver the required electrical current to your power tool.
Every foot of cord increases the electrical resistance, which decreases the power the cord can deliver to your tool. So, the longer the cord, the lower its capacity to carry the current.
This means that a cord with a specific gauge may be suitable for powering a high-wattage power tool over a shorter distance, but the same cord may only be able to safely power a lower-wattage power tool if it needs to cover a longer distance.
And this is why you should only buy an extension cord no longer than is needed. So, buy only the length you need. The shorter the better. Why buy a 100-feet cord to power your electric chainsaw if your yard is no further than 45 feet in any direction? Don’t do that. It doesn’t make any sense and it will compromise the power delivered to your chainsaw.
General Extension Cord Gauge Guidelines
If you are unable to locate the manufacturer’s gauge recommendations for your specific power tool, the following tables (source: The Home Depot) provide a general guide to help you determine the minimum extension cord requirements based on the tool’s amperage and the desired cord length.
25 ft Extension Cords
| Device Amp | Gauge |
|---|---|
| 1-13A | 16 Gauge (Light Duty) |
| 14-15A | 14 Gauge (Medium Duty) |
| 16-20A | 12 Gauge (Heavy Duty) / 10 Gauge (Extra Heavy Duty) |
50 ft Extension Cords
| Device Amp | Gauge |
|---|---|
| 1-13A | 16 Gauge (Light Duty) |
| 14-15A | 14 Gauge (Medium Duty) |
| 16-20A | 12 Gauge (Heavy Duty) / 10 Gauge (Extra Heavy Duty) |
100 ft Extension Cords
| Device Amp | Gauge |
|---|---|
| 1-10A | 16 Gauge (Light Duty) |
| 11-13A | 14 Gauge (Medium Duty) |
| 14-15A | 12 Gauge (Heavy Duty) |
| 16-20A | 10 Gauge (Extra Heavy Duty) |
Although these guidelines are fairly standard not everyone agrees on what’s best. To be on the safe side we recommend going one step down in gauge (thicker inner wires). For example, for a 15-amp electric chainsaw the chart suggests you buy a 14-gauge 50-feet cord or 12-gauge 100-feet cord but we recommend to go for a 12-gauge 50-feet cord, and 10-gauge 100-feet cord.
Final Thoughts
The best outdoor extension cord is always the one suited to the tool you’re using. While it may be tempting to save a few dollars on a cheaper cord, doing so could come at a significant cost in the long run.
If you buy the wrong extension cord you may pay the price in other ways, like burning out your tool prematurely, or even worse, creating a fire hazard. Honestly, it’s not worth the few extra dollars.
Make sure you read the owner’s manual to find out what the manufacturer recommends – and never go below their recommendations. Follow the guidelines and always choose safety first.
