How To Choose Extension Cords

Extend the reach for powering your appliances and devices with heavy duty extension cords

Extension cords allow you to power a device when its own cable does not reach an electrical outlet. This guide will help you understand the differences between extension cords to ensure safety, energy efficiency and top performance.

Indoor vs. Outdoor Extension Cords

Outdoor extension cords have tough covers made from rubber, plastic or vinyl. Using indoor extension cords outside can lead to overheating.

Tip: Some heavy-duty cords are rated for protection against oils, chemicals or extreme temperatures.

Outdoor extension cords fall into three broad categories:  

  • Occasional use cords are suitable for smaller projects and tools.
  • Frequent use cords can handle larger tools and equipment and heavier use.
  • Rugged cords are designed for continual use on job sites, even in extreme weather, and are suitable for high-amperage tools.

Designation Letter Meaning

S

Indicates a flexible cord designed for general use

W

Indicates the cord is rated for outdoor use

J

Indicates the cord with standard 300 voltage insulation. If there is no J in the designation, the cord has thicker, 600-volt insulation, designed for heavier use.

P

Indicates parallel wire construction, used in  air conditioner cords and household extension cords

T

Indicates the cord jacket is made from vinyl thermoplastic

E

Indicates the cord jacket is made from thermoplastic elastomer rubber (TPE)

O

Indicates the cord is oil-resistant

Plug Type

Extension cords typically come with two- or three-prong plugs, while others have specialty receptacles and plugs for RVs and construction applications.

The third prong in the extension cord provides a path to the ground wire in a household electrical circuit. This ground wire greatly reduces the risk of electrical shock and fires. The three-prong cord itself should only be used with properly grounded three-slot outlets.

Amperage, Gauge & Cord Length

Each extension cord has a maximum amperage — the limit on the current it can conduct safely. Connecting devices with a higher current, may cause overheating.

Tip: You can usually find the energy requirements for electrical devices listed on the device itself or in the instruction manual.

If you plan to connect multiple devices to the cord at the same time, add up the current requirements for each device. The power requirements for some devices are listed in watts, rather than amps. Use this formula to convert the rating to amps: Amps = watts/110.

If an extension cord doesn't include a maximum amperage rating, you can figure out its capacity by looking at its American Wire Gauge (AWG) rating. A lower AWG number indicates a thicker wire and a higher capacity, so the lower the number, the higher the cord's capacity to deliver power.

Gauge is typically listed along with the number of conducting wires in the cord. For example, a 14/3 cord contains 14-gauge wire and has three conductions inside.

Typically, you can find a cord's gauge rating printed on the cord jacket. If you're replacing an old cord, look for the AWG number printed on the jacket, and select a new cord with the same gauge. 

extension-cords-jacket

To determine the cord's capacity, consider the cord length along with the wire gauge. Every extra foot of cord increases the electrical resistance, which decreases the power the cord can deliver to connected devices. Because of this, it's best to use a cord that is only as long as you need.  

Cord Length Device Amperage Rating Good for Use with Minimum Wire Gauge
  • 25 Feet
  • 1 – 13 Amps
  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers
  • 16 Gauge
    (Light Duty)
  • 25 Feet
  • 14 – 15 Amps
  • Lawn mowers
  • Power drills
  • Table saws
  • 14 Gauge
    (Medium Duty)
  • 25 Feet
  • 16 – 20 Amps
  • Chain saws
  • Circular saws
  • Shop vacs
  • Air Compressors
  • 12 Gauge
    (Heavy Duty)
    or 10 Gauge
    (Extra Heavy Duty)
  • 50 Feet
  • 1 – 13 Amps
  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers
  • 16 Gauge
    (Light Duty)
  • 50 Feet
  • 14 – 15 Amps
  • Lawn mowers
  • Power drills
  • Table saws
  • 14 Gauge
    (Medium Duty)
  • 50 Feet
  • 16 – 20 Amps
  • Chain saws
  • Circular saws
  • Shop vacs
  • 12 Gauge
    (Heavy Duty)
    or 10 Gauge
    (Extra Heavy Duty)
  • 100 Feet
  • 1 – 10 Amps
  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers
  • 16 Gauge
    (Light Duty)
  • 100 Feet
  • 11 – 13 Amps
  • Lawn mowers
  • Power drills
  • Table saws
  • 14 Gauge
    (Medium Duty)
  • 100 Feet
  • 14 – 15 Amps
  • Chain saws
  • Circular saws
  • Shop vacs
  • 12 Gauge
    (Heavy Duty)
  • 100 Feet
  • 16 – 20 Amps
  • Air compressors
  • 10 Gauge
    (Extra Heavy Duty)
  • 150 Feet
  • 1 – 7 Amps
  • Christmas lights
  • Work lights
  • Portable fans
  • 14 Gauge
    (Medium Duty)
  • 150 Feet
  • 8 – 10 Amps
  • Lawn mowers
  • Power drills
  • 12 Gauge
    (Heavy Duty)
  • 150 Feet
  • 11 – 15 Amps
  • Table saws
  • Chain saws
  • Circular saws
  • Shop vacs
  • 10 Gauge
    (Extra Heavy Duty)

Features

There are extension cords with a GFCI, lighted plug, connector box, multiple sockets and more depending upon your needs.  

  • Built-in ground fault circuit interrupter (GFCI): A device that automatically shuts power to the extension cord in the event of a ground fault.
  • Lighted plug: A plug that lights up to indicate when the cord is powered.
  • Connector box: A device that fits around both the extension cord plug and the plug on the connected electrical device to keep them from pulling apart.
  • Locking socket: A locking mechanism built into the extension cord socket that keeps the device and cord securely connected.
  • Multiple sockets: Cords that allow you to power multiple devices at once.
  • Safety listing: A guarantee that an independent testing agency, such as Underwriters Laboratories (UL mark), Intertek (ETL mark) or the Canadian Standards Association (CSA mark), has ensured that an extension cord is safe for its rated use.