Buying Guide

Extension Cords Buying Guide

Indoor vs. Outdoor Extension Cords

A coiled extension cord.

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

A three-prong plug extension cord.

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

An AWG rating stamped on the jacket of an extension cord.

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.


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 Lengths and Amperage Ratings

A person pushing a lawn mower attached to an extension cord.

25 Feet

Device Amperage Rating:  1 – 13 Amps

Good for use with:

  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers

Minimum Wire Gauge: 16 Gauge (Light Duty)


25 Feet

Device Amperage Rating: 14 – 15 Amps

Good for use with:

  • Lawn mowers
  • Power drills
  • Table saws

Minimum Wire Gauge: 14 Gauge (Medium Duty)


25 Feet

Device Amperage Rating: 16 – 20 Amps

Good for use with:

  • Chain saws
  • Circular saws
  • Shop vacs
  • Air Compressors

Minimum Wire Gauge: 12 Gauge (Heavy Duty) or 10 Gauge (Extra Heavy Duty)


50 Feet

Device Amperage Rating: 1 – 13 Amps

Good for use with:

  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers

Minimum Wire Gauge: 16 Gauge (Light Duty)


50 Feet

Device Amperage Rating: 14 – 15 Amps

Good for use with:

  • Lawn mowers
  • Power drills
  • Table saws

Minimum Wire Gauge: 14 Gauge (Medium Duty)


50 Feet

Device Amperage Rating: 16 – 20 Amps

Good for use with:

  • Chain saws
  • Circular saws
  • Shop vacs

Minimum Wire Gauge: 12 Gauge (Heavy Duty) or 10 Gauge (Extra Heavy Duty)


100 Feet

Device Amperage Rating: 1 – 10 Amps

Good for use with:

  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers

Minimum Wire Gauge: 16 Gauge (Light Duty)


100 Feet

Device Amperage Rating: 11 – 13 Amps

Good for use with:

  • Lawn mowers
  • Power drills
  • Table saws

Minimum Wire Gauge: 14 Gauge (Medium Duty)


100 Feet

Device Amperage Rating: 14 – 15 Amps

Good for use with:

  • Chain saws
  • Circular saws
  • Shop vacs

Minimum Wire Gauge: 12 Gauge (Heavy Duty)


100 Feet

Device Amperage Rating: 16 – 20 Amps

Good for use with:

  • Air compressors

Minimum Wire Gauge: 10 Gauge (Extra Heavy Duty)


150 Feet

Device Amperage Rating: 1 – 7 Amps

Good for use with:

  • Christmas lights
  • Work lights
  • Portable fans

Minimum Wire Gauge: 14 Gauge (Medium Duty)


150 Feet

Device Amperage Rating: 8 – 10 Amps

Good for use with:

  • Lawn mowers
  • Power drills

Minimum Wire Gauge: 12 Gauge (Heavy Duty)


150 Feet

Device Amperage Rating: 11 – 15 Amps

Good for use with:

  • Table saws
  • Chain saws
  • Circular saws
  • Shop vacs

Minimum Wire Gauge: 10 Gauge (Extra Heavy Duty)

Features

A green extension cord with a UL mark indicated.

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 shutsdown 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.


Extension Cord Safety Tips

A safely stored extension cord neatly coiled on a shelf.
  • Extension cords should only be used as a temporary electric solution, and they must be unplugged when not in use.
  • Use the correct extension cord for the purpose; outdoor-rated cords should not be used indoors and vice versa.
  • Never plug one extension cord into another or overload a cord.
  • Store all extension cords indoors in a cool, dry place, and never use a wet extension cord.
  • Do not drive over or place carpet or rugs over an extension cord in use.
  • Be sure the extension cord is fully seated into the socket before you connect anything to it; however, never force an extension cord into a socket where it does not fit.

Surge Protectors vs. Extension Cords

A surge protector.

While an extension cord merely provides additional reach for your electrical device, a surge protector can be a device saver. Surge protectors prevent electrical spikes or power surges from damaging expensive electronic equipment. Power surges and spikes can send many more volts through the systems of your electronics than the devices can safely be exposed to. A surge protector absorbs the energy and directs it away from the devices you attach to it. This gives it an advantage over a simple extension cord, which might not offer the same protection.


There are surge protectors available in power strips and as wall-mounted units to protect individual devices in the home. However, professional electricians can also install a whole-home surge protector at the service panel. 


Surge protectors are limited in their protection capacity. All surge protectors come with a joule rating. This indicates how much energy the device can deflect before it become vulnerable to failure. Many surge protectors have indicator lights that indicate when they should be replaced, but as a rule, a new surge protector every two years should ensure your electronics stay safe.