Things You Should Know Before Buying an Extension Cord

by Becky BlantonApril 24, 2018

We all have at least one extension cord, but is it the right one, or even the best one, for what you need it for? To the average consumer, an extension cord is an extension cord. Most of us don’t understand the differences in things like wire gauge (size) or environment (indoor or outdoor or both), or purpose (extended use for a power tool or other device that will be left on for long periods of time, or for short-term use such as running a vacuum cleaner, or shop-vac). Another thing consumers fail to realize is that regardless of the gauge or rating of the cord, an extension cord is always a temporary solution. Extension cords were never meant to be used as a long-term extension of your household’s electrical system. If you don’t have an outlet where you need it, you’re better off, in the long run, having a licensed electrician install another outlet and the proper connections to run whatever appliance you need to run in that location.

What is an extension cord?

An extension cord is usually simply a cord with a plug on one end and an outlet on the other. Depending on the gauge of the cord, it may or may not have wires of a thick enough gauge to carry the full current (usually 15 amps) that a home’s main electrical circuit is rated for, at least not for long-term use.

Wire gauge matters

Not all extension cords can be used for all purposes. There are generally three kinds of extension cords – light or occasional use, medium to frequent use, and heavy duty or rugged. These terms refer to the cord’s wire gauge. The gauge of wire indicates whether the cord can be used for heavy-duty or continuous use, such as power tools, computers, heaters etc., and not necessarily whether it can be used indoors or outdoors, although most heavy duty extension cords tend to be outdoor rated cords. Gauge numbers can be confusing. The larger the gauge number, the smaller the cord’s actual gauge. Most common gauges are American Wire Gauge (AWG) AWG 16, AWG 14, AWG 12, AWG 10, and AWG 8. The lower the number, the thicker the wire, or bundle of wire, and the thicker the wire, the more watts you can expect to power through it. So a 10-12 gauge cord would be a heavier duty cord than a 16-gauge cord, which would be a lightweight cord typically used for less energy demanding applications.

Indoor vs. Outdoor Extension Cords

Outdoor extension cords have tough covers made from rubber, plastic, or vinyl. Using indoor extension cords outdoors can lead to overheating, electrocution, cord failure, or fire. So what should you know before you buy? Know what you intend to use the cord for and whether you intend to use it indoors or outdoors.

  • Occasional use cords. Occasional use cords are very lightweight, light gauge 16-gauge extension cords. They’re suitable for light duty indoor applications, like running holiday lights, portable fans, your electric hedge trimmers, or your vacuum cleaner.
  • Frequent use cords. A 14-gauge cord is for medium or frequent duty applications (lawnmowers, power drills, table saws, television sets, etc.). These cords are also great for things like power tools, electric chainsaws, leaf or snow blowers, etc. They can handle larger tools and equipment and heavier use. Business Insider recommends the Coleman 16 Gauge Extension Cord. It delivers 1,250 watts of power 100 feet away from the outlet, enabling it to easily run most power and lawn tools over a continuous amount of time.
  • Rugged cords. A 10- to 12-gauge cord is for heavy and extra heavy duty applications (chainsaws, circular saws, shop vacs, air compressors, etc.). These are the heavier weight, and heavier duty cords designed for continual use on job sites, even in extreme weather, and are suitable for very high-amperage tools. According to Wirecutter, a New York Times company that reviews and lists the best gear and gadgets for people who want to save the time and stress of figuring out what to buy, the 50-foot Voltec Yellow Outdoor Extension Cord has the most durable strain-relief neck, the strongest and smoothest connection, and has a rugged outer jacket — making it the longest lasting outdoor extension cord they tested.

Also look for the designation letter:

  • S: Indicates a flexible cord designed for general use
  • W: Indicates the cord is rated for outdoor use
  • J: Indicates the cord has 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

Items that should never be connected to an extension cord

Using light or medium weight extension cords on high energy usage items is almost always a fire hazard. Because extension cords are almost never the right size most people coil the extra cord up and place it behind the unit. The coil retains heat, melts the covering on the cord and eventually catches fire. Things you should never plug into an extension cord:

  • Hair Dryers – Hair dryers typically draw 15 amps, which can cause an extension cord to get hot enough to start a fire.
  • Irons – Heat-producing appliances like irons, draw at least 10-12 amps of current, which is beyond the limits of most indoor extension cords.
  • Coffee Pots – Heat-producing appliances like coffee pots draw at least 10-12 amps of current, which is beyond the limits of most indoor extension cords.
  • Toaster – Heat-producing appliances like toasters draw at least 10-12 amps of current, which is beyond the limits of most indoor extension cords. Hopefully your kitchen layout permits the small, portable appliances to live near an outlet, far from the sink.
  • Treadmills – Treadmill manufacturers generally discourage the use of an extension cord with the product. But if you can’t move your exercise equipment closer to the outlet, go with a cord made specifically for treadmills, like the 9-foot Treadcord.
  • Space or portable heaters – Portable heaters are not safe for use with an extension cord. Space heaters are portable—move them closer to an outlet.

Furthermore, be mindful that heat appliances draw much more power than non-heat appliances.

Tips on selecting and using extension cords safely

  • Only buy extension cords that have been approved by an independent testing laboratory.
  • Only use extension cords marked for outdoor use for outdoor projects.
  • Before using any extension cord read the instructions (if available) for information about the cord’s correct use and the amount of power it draws.
  • Select cords that are rated to handle the wattage of the devices with which they’ll be used. A cord’s gauge indicates its size: The smaller the number, the larger the wire and the more electrical current the cord can safely handle.
  • Longer extension cords can’t handle as much current as shorter cords of the same gauge, so use the shortest possible cord to get the best electrical current.
  • Choose cords with polarized or three-prong plugs.
  • Thick, round, low-gauge extension cords are best for large appliances and tools. For smaller appliances and electronics, you can use thin or flat extension cords.
Shares 0
About The Author
Becky Blanton
Becky Blanton is a full-time ghostwriter and writing coach for Fortune 500 companies, CEOs, and business speakers. In 2009 she spoke at TED Global at Oxford University, her first ever public speaking gig. When she's not writing, she's kayaking in the Chesapeake Bay. Her dream home is to live aboard a sailing or houseboat.