Extension cord safety tips

Aug. 27, 2009
Reduce risk of extension cord-generated fire, electrical shock and property damage.

When in need of an extension cord, remember that just because a particular cord is long enough, doesn't mean that it's the right one for the job. Many people erroneously believe that length is the only characteristic that sets one extension cord apart from another, but there’s far more that should be considered.

All power extension cords are not created equal. They are manufactured to carry varying amounts of electrical current in specific applications and environments. By basing your extension cord choice on each task’s specific requirements, you can greatly reduce the risk of fire, electrical shock and injury that come with improper use.

Here are some helpful extension cord safety tips:

Classifications — Extension cords are classified for either indoor or outdoor use. The insulation, or jacket, of an outdoor-rated extension cord is made of a tougher material, which is designed to withstand temperature changes, moisture, UV rays and sometimes chemicals. While it’s fine to use an outdoor power cord indoors, never use an indoor-rated extension cord for an outside job. Doing so could cause electric shock or create a fire hazard.

Wattage rating — The number of watts an extension cord can safely transmit (given its length and gauge) is known as a wattage rating. Before plugging an appliance or power tool into an extension cord, it’s important to be sure that the power demand (or pull) of that device doesn’t exceed the cord’s wattage rating.

Powering multiple devices — If you plan to plug more than one device into a given extension cord, calculate the devices' combined energy requirements and make sure that the total isn’t higher than the wattage rating for the cord. Never use an extension cord to supply more wattage than it’s rated for since overheating and fire may occur.


Gauge and distance — Any electrical or extension cord contains an inner metal conducting wire that carries electrical current from one end to the other. The thickness of this conductor is referred to as its gauge. Gauge is indicated by a number; the lower the number, the thicker the wire is. A wire’s thickness directly affects the amount of current (or wattage) it can carry over a certain distance.

Power requirements — It’s important to know how much electricity is required to run a given device before you plug it in. For the most part, you won’t need to do more than consult the manufacturer’s instructions. Another good place to look for wattage specs is on the tag that is often attached to a device’s power cord. If all else fails, a quick call to the product’s manufacturer should clear up any questions.

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Amps/volts vs. watts — In some cases, you may find power requirements listed in amps and volts instead of watts. For these situations, there’s a simple formula that can help you calculate electricity requirements: Multiply the number of amps by the number of volts. The resulting number equals that appliance’s wattage. Here’s an example: If a device uses 5 amps at 110 volts, that translates into 550W (5 x 110 = 550).

UL approval — When shopping for extension cords, only purchase those that bear the UL symbol. The presence of the UL mark tells you that samples of that particular type of cord have been tested by Underwriters Laboratories and received consumer safety approval.

Red flags — Don’t use extension cords with cut or damaged insulation. Exposed conducting wires can put you at risk for fire, burns and electrical shock.

Alterations — Do not cut, file or otherwise alter an extension cord’s grounding pin or plug blades to make it easier to plug into an outlet. If the extension cord plug doesn’t fit into an older outlet, have an electrician replace the receptacle.

Unplugging — Regardless of whether or not it’s being used, as long as a power extension cord is plugged into an outlet, it’s conducting electricity. To avoid potential safety hazards, always remember to unplug extension cords when they’re not in use.

Storage — Extended exposure to outdoor conditions can cause cords to deteriorate. Whether they’re rated for indoor or outdoor use, store all extension cords inside when they’re not in use.

Christina Hansen is a Product Specialist at She may be reached through the company’s Web site at

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