Buying Guide

Best Extension Cords for Any Situation

Indoor vs. Outdoor Extension Cords
Extension cords powering items indoors and out.

The difference between outdoor extension cords and indoor extension cords is construction based on use. Most indoor cords are generally thinner, shorter and less powerful than outdoor options. Outdoor extension cords are designed with a thick, durable layer of protective insulation. They can also come in much longer lengths and carry more current. 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.


Tip: Outdoor cords can be used indoors but do not use indoor cords outside. 

What is Designation Lettering?
An extension cord displaying its AWG information.

Extension cords have a sequence of letters on their insulation or jackets. These letters indicate the designated use for the extension cord based on the type of wire inside the cord. For example, some heavy-duty extension cords are rated for protection against oils, chemicals or high temperatures.


Refer to the letters below when choosing the best extension cords for a task. 


  • An "S" cord is flexible and designed for general use.
  • A "W" cord is rated for outdoor use
  • A "J" cord has a standard 300-volt insulation. If there is no J in the designation, the cord has thicker, 600-volt insulation, designed for heavier use.
  • A "P" cord has a parallel wire construction, used in air conditioner cords and household extension cords
  • An "T" cord jacket is made from vinyl thermoplastic
  • An "E" cord jacket is made from thermoplastic elastomer rubber (TPE)
  • An "O" cord is oil-resistant.
  • An "FT2" cord is flame retardant.
  • A "CL2S" wire is designed for in-wall construction.
  • An "SRDT" wire is heavy duty and good for high amperage products.
  • An "HPN" the cord’s performance won’t be affected by the high temperatures associated with appliances.  



Amperage, Gauge & Cord Length
An outdoor extension cord coiled on the ground.

Choosing the best outdoor extension cord or indoor cord relies on understanding how amperage, cord length and gauge ratings work together. Each one of these attributes affects the performance and power of an extension cord. 


Amperage is how much power (or amps) a cord is made to handle. For example, high-amperage appliance extension cords are designed to carry 20 amps or more. 


All extension cords have an AWG (American wire gauge) rating. This rating is a standardized wire gauge system for measuring electrical wire. A lower AWG number indicates a thicker wire and a higher capacity. 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.


Extension cord lengths determine the cord’s power capacity. Every extra foot of cord increases the electrical resistance. This decreases the power the cord can deliver to connected devices. For best results, use the shortest extension cord possible.


Tip: If you're replacing an old cord, look for the AWG number printed on the jacket to select a new cord with the same gauge. 

Best Uses for 25-foot & 50-foot Extension Cords
A holiday-themed extension cord powering a Christmas tree.

25-Foot/Device Amperage Rating:  1 – 13 Amps

  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers
  • Minimum Wire Gauge: 16 Gauge (Light Duty)

25-Foot/Device Amperage Rating: 14 – 15 Amps

  • Lawn mowers
  • Power drills
  • Table saws
  • Minimum Wire Gauge: 14 Gauge (Medium Duty)

25-Foot/Device Amperage Rating: 16 – 20 Amps

  • Chain saws
  • Circular saws
  • Shop vacs
  • Air compressors
  • Minimum Wire Gauge: 12 Gauge (Heavy Duty) or 10 Gauge (Extra Heavy Duty)

50-Foot/Device Amperage Rating: 1 – 13 Amps

  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers
  • Minimum Wire Gauge: 16 Gauge (Light Duty)

50-Foot/Device Amperage Rating: 14 – 15 Amps

  • Lawn mowers
  • Power drills
  • Table saws
  • Minimum Wire Gauge: 14 Gauge (Medium Duty)

50-Foot/Device Amperage Rating: 16 – 20 Amps

  • Chain saws
  • Circular saws
  • Shop vacs
  • Minimum Wire Gauge: 12 Gauge (Heavy Duty) or 10 Gauge (Extra Heavy Duty)


Best Uses for 100-foot & 150-foot Extension Cords
Someone using a leaf blower attached to an outdoor extension cord.

100-foot/Device Amperage Rating: 1 – 10 Amps

  • Christmas lights
  • Work lights
  • Portable fans
  • Hedge trimmers
  • Minimum Wire Gauge: 16 Gauge (Light Duty)

100-foot/Device Amperage Rating: 11 – 13 Amps

  • Lawn mowers
  • Power drills
  • Table saws
  • Minimum Wire Gauge: 14 Gauge (Medium Duty)

100-foot/Device Amperage Rating: 14 – 15 Amps

  • Chain saws
  • Circular saws
  • Shop vacs
  • Minimum Wire Gauge: 12 Gauge (Heavy Duty)

100-foot/Device Amperage Rating: 16 – 20 Amps

  • Air compressors
  • Minimum Wire Gauge: 10 Gauge (Extra Heavy Duty)


150-foot/Device  Amperage Rating: 1 – 7 Amps

  • Christmas lights
  • Work lights
  • Portable fans
  • Minimum Wire Gauge: 14 Gauge (Medium Duty)

150-foot/Device/Amperage Rating: 8 – 10 Amps

  • Lawn mowers
  • Power drills
  • Minimum Wire Gauge: 12 Gauge (Heavy Duty)

150-foot/Device Amperage Rating: 11 – 15 Amps

  • Table saws
  • Chain saws
  • Circular saws
  • Shop vacs
  • Minimum Wire Gauge: 10 Gauge (Extra Heavy Duty)


Tip: Find the amp needs for most electrical devices on the device or in the instruction manual. 


Plug Types
Someone connecting an extension cord.

Extension cords typically come with two- or three-prong plugs. Specialty cords for high amperage devices and uses such as RVs and construction tools have additional receptacles. 


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.


Tip: Connecting devices with a higher current may cause overheating. Check the maximum amperage each extension cord can conduct safely. 


Special Extension Cord Features
A new extension cord wrapped in packaging.

Extension cords can have special features that help them work better and safer. These features include a GFCI, lighted plug, connector box, multiple sockets or more.


  • A GFCI (Built-In Ground Fault Circuit Interrupter) device automatically shuts down power to the extension cord in the event of a ground fault.

  • A lighted plug lights up to indicate when the cord is powered.

  • A connector box is a device that fits around both plugs. It connects the cord and device to keep them from pulling apart.

  • Some of the best outdoor extension cords feature a locking socket. This mechanism is built into the extension cord socket. It keeps the device and cord securely connected. 
  • Multiple sockets allow you to safely power multiple devices at once.



Surge Protectors vs. Extension Cords
A white surge protector featuring a black cord.

An extension cord extends the reach for your electrical device. A surge protector prevents electrical spikes or power surges from damaging expensive electronic equipment. Power surges can occur during storms or when a large appliance such as an air conditioner comes on or cycles up. 


Power surges and spikes send more volts through electronics and appliances than they can safely handle. A surge protector absorbs the energy and directs it away from the devices it’s attached to. 


A surge protector’s joule rating indicates how much energy it can absorb. Joule ratings can go from 200 to 1000. The higher a surge protector’s joule rating, the more protection it offers. For expensive devices, consider using a surge protector with a fairly high joule number. 


Tip: Surge protectors are available in power strips and as wall-mounted units. They protect individual devices in the home. Professional electricians can install a whole-home surge protector in the master service panel.


Extension Cord Safety
An orange extension cord featuring a three-prong end.
  • Always use the correct extension cord for the purpose. Indoor-rated cords should not be used outdoors. 
  • Never plug one extension cord into another or overload a cord.
  • Store all extension cords indoors in a cool, dry place. 
  • 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.
  • The best extension cords for smaller RVs are usually 30 amps while larger ones can require 50 amps. Consult your owner’s manual for specifics.
  • Look for safety listings from independent testing agencies such as Underwriters Laboratories (UL), Intertek (ETL) or the Canadian Standards Association (CSA mark) to make sure an extension cord is safe for its rated use.


Always choose the best extension cord for the location and the device. The right extension cord will give you the power you need, when you need it. It extends the reach of power tools and makes it easier to put devices where you want them. 


Remember, extension cords should only be used as a temporary electric solution. Unplug them when not in use. Make sure to always use a surge protector to protect expensive devices or equipment. Ready to buy a surge protector and outdoor or indoor extension cord? The Home Depot delivers online orders when and where you need them.