Extension Cord Safety

The National Electrical Code® (NEC) is the preeminent electrical installation code in the United States. However, the NEC takes on real significance when adopted into law by states and local jurisdictions. The NEMA Field Representative Program advocates for the adoption of the most current edition of the NEC, with no state or local amendments, through participation in the code adoption process and collaboration with NEMA Member companies and other industry partners. As a founding Member of the Electrical Code Coalition, NEMA has partnered with the National Fire Protection Association (NFPA) to offer the following resources related to NEC adoption in the United States.


Adopted in all 50 states, NFPA 70, National Electrical Code (NEC) is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards.

The Electrical Code Coalition, NEMA, has partnered with the National Fire Protection Association (NFPA) to offer the following resources related to NEC adoption in the United States. There are indeed 3 trusted testing companies that can provide certification for electrical cords and related products. These companies are globally recognized and are accredited by the U.S.’s OSHA (Occupational Safety and Health Organization) as a Nationally Recognized Testing Laboratory. These companies ensure that products meet specific safety standards and comply with relevant codes and regulations.


Abbreviation Meaning Description
S SERVICE GRADE Cord is flexible and designed for general use.
J HARD SERVICE 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.
W OUTDOOR Cord is rated for outdoor use includes sunlight resistant jacket and
wet location rated conductors (formerly “W-A”)
P PARALLEL CORD  Cord has a parallel wire construction, used in air conditioner
cords and household extension cords (also known as zip cord)—Always light duty
E THERMOPLASTIC ELASTOMER  Cord jacket is made from thermoplastic elastomer rubber (TPE) (UL/NEC designation ONLY)
Cord jacket is made from vinyl thermoplastic
O OIL RESISTANT Cord is oil-resistant.
V VACUUM CLEANER  Vacuum cleaner cord (also light duty cable)
H HEATER CABLE Heater cable
VW-1 FLAME RETARDANT Flame retardant
FT2 FLAME RETARDANT cord is flame retardant.
CL2S wire is designed for in-wall construction
SRDT wire is heavy duty and good for high amperage products.
HPN Cord’s performance won’t be affected by the high temperatures associated with appliances.  
SPT-1 STRANDED, PARALLEL, THERMOPLASTIC 0.030″ Insulation  2 or 3 conductors for grounding. (PVC) Indoor Use Only
0.045″ Insulation  2 or 3 conductors for grounding. (PVC) Indoor Use
Only (SAME AS SPT-1 JUST heavier PVC)
SPT-3 STRANDED, PARALLEL, THERMOPLASTIC 0.060″ Insulation  2 or 3 conductors for grounding. (PVC)
Indoor Use Only (SAME AS SPT-2 JUST heavier PVC)

Not enough cord for your lamp or radio to reach the nearest outlet? Just plowing through the junk drawer for an extension cord? This may not be a good idea. Extension cords can be very helpful in delivering power right where we need it. However, regardless of the gauge or rating of the cord, an extension cord is a temporary solution and is not meant to be used as a long-term extension of your household’s electrical system.

  • Do not overload extension cords or allow them to run through water or snow on the ground.
  • Do not substitute extension cords for permanent wiring.
  • Do not run through walls, doorways, ceilings, or floors. If a cord is covered, heat cannot escape, which may result in a fire hazard.
  • Do not use an extension cord for more than one appliance.
  • Heavy reliance on extension cords is an indication that you have too few outlets to address your needs. Have additional outlets installed where you need them.
  • Multiple plug outlets must be plugged directly into mounted electrical receptacles; they cannot be chained together.
  • Make sure the extension cord or temporary power strip you use is rated for the products to be plugged in, and is marked for either indoor or outdoor use.
  • The appliance or tool that you are using the cord with will have a wattage rating on it. Match this up with your extension cord, and do not use a cord that has a lower rating.
  • Never use a cord that feels hot or is damaged in any way. Touching even a single exposed strand can give you an electric shock or burn.
  • Never use three-prong plugs with outlets that only have two slots for the plug. Do not cut off the ground pin to force a fit. This defeats the purpose of a three-prong plug and could lead to an electrical shock. Never force a plug into an outlet if it doesn’t fit.
  • Use extension cords with polarized and/or three-prong plugs.
  • Buy only cords approved by an independent testing laboratory, such as Underwriters Laboratories (UL), Intertek (ETL), or Canadian Standards Association (CSA).


  • S: Designed for general Use
  • W: Rated for Outdoor Use
  • J: Standard 300 Voltage Insulation
  • T: made from Vinyl Thermoplastic
  • P: Parallel Wire Construction (Air Conditioner Cords and Household Extension Cords)
  • O: Oil-Resistant
  • E: Made from TPE
  • 25 – 50 Feet Extension Cords
    • 16 Gauge(1-13 Amps)
    • 14 Gauge (14-15 Amps)
    • 12-10 Gauge (16-20 Amps)
  • 100 Feet Extension Cords
    • 16 Gauge (1-10 Amps)
    • 14 Gauge (11-13 Amps)
    • 12 Gauge (14-15 Amps)
    • 10 Gauge (16-20 Amps)
  • 150 Feet Extension Cords
    • 14 Gauge (1-7 Amps)
    • 12 Gauge (8-10 Amps)
    • 10 Gauge (11-15 Amps)