Extension Cord

What it is

An extension cord is a portable, flexible power cable with a plug on one end and one or more receptacles on the other. It lets you temporarily extend access to electricity beyond the reach of a wall outlet. Cords are labeled for indoor or outdoor use and come in different wire sizes (gauges), lengths, and features that determine how much power they can carry safely and how well they perform over distance.

Common DIY and Home Uses

Extension cords show up in many day‑to‑day tasks:

• Powering lawn equipment, like corded mowers, trimmers, and leaf blowers
• Running a shop vacuum, circular saw, or sander in a garage or driveway
• Plugging in holiday lights or inflatable decorations outside
• Temporarily powering a sump pump during maintenance or a dehumidifier in the basement
• Connecting work lights in attics, crawlspaces, or sheds
• Setting up a temporary workstation for painting or drywall work

Because extension cords are for temporary power, they should be used for the duration of a task and then unplugged and stored.

Types and Ratings

Choosing the right cord starts with understanding the labels and construction.

• Indoor vs. Outdoor

  • Indoor cords: Usually lighter, thinner jackets, often white or brown. Marked with designations like SPT (flat lamp cords). Meant for dry, indoor areas only.
  • Outdoor cords: Thicker, durable jackets to resist moisture, UV, and abrasion. Look for markings like SJTW (general outdoor) or SJEOW (more flexible in cold).

• Gauge (AWG) and Amps

  • Wire size is measured in AWG (American Wire Gauge). Lower numbers mean thicker wire that carries more current with less voltage drop.
  • Common sizes: 16 AWG (light duty), 14 AWG (medium duty), 12 AWG (heavy duty). For long runs or high‑draw tools, go thicker (lower AWG).

• Length and Voltage Drop

  • Longer cords increase resistance, which reduces voltage at the tool. That can make motors run hot and underperform. If you need a long reach, pick a thicker gauge to compensate, or use the shortest cord that gets the job done.

• Number of Outlets and Features

  • Single vs. triple‑tap ends: A multi‑outlet end is convenient for light loads; avoid overloading.
  • GFCI cords: Built‑in Ground‑Fault Circuit Interrupter for use outdoors or in damp locations.
  • Lighted ends: A small indicator light shows the cord is powered.
  • Locking connectors: Help keep tool plugs from pulling out.
  • Flat plug/low‑profile: Useful behind furniture.
  • Cord reels: Keep storage tidy; use only fully unspooled under heavy load to prevent heat buildup.

• Specialty cords

  • Appliance cords: Short, heavy‑duty, grounded cords for brief use with refrigerators or window A/C units during maintenance moves. Many manufacturers advise plugging such appliances directly into a wall outlet.
  • Generator cords: Heavy, weather‑rated cords designed to connect to transfer switches or inlet boxes. Never backfeed a home through a dryer outlet.

How to Choose the Right Cord

Follow this simple process:

1. Check the load: Find the tool or appliance’s amps or watts. If you have watts, divide by 120 to estimate amps (Watts ÷ 120 = Amps in North American homes).
2. Match the gauge:
   • Up to about 7 amps and short lengths: 16 AWG may suffice (lamps, phone chargers).
   • 8–12 amps or moderate lengths: 14 AWG (many power tools, shop vacs).
   • 13–15 amps, longer runs, or continuous loads: 12 AWG.
3. Pick the shortest length that reaches comfortably without pulling tight.
4. Choose indoor or outdoor based on the environment. If moisture is possible, use a weather‑rated cord and GFCI protection.
5. Confirm grounding: Use a 3‑prong cord for 3‑prong tools. Never remove the ground pin.
6. Add helpful features: Lighted ends, locking collars, or a cord reel if it fits your workflow.

Safe Use and Care

• Inspect before each use: Look for cuts, cracked jackets, loose blades, or a missing ground pin. Replace damaged cords—don’t tape over defects.
• Fully uncoil under load: Heat can build up in coiled cords. Lay the cord out straight or in large loose loops when powering high‑draw tools.
• Keep dry and elevated: Use outdoor‑rated cords only outside; keep connections off wet ground. Plug into a GFCI outlet or use a GFCI cord in damp areas.
• Avoid pinch points: Don’t run cords through doorways, under rugs, or across sharp edges. Use cord covers where foot traffic is unavoidable.
• Don’t daisy‑chain: Using multiple cords end‑to‑end raises resistance and trip risk. Use one appropriately sized cord.
• Respect the rating: Don’t exceed the cord’s amp rating or the branch circuit (often 15A). High‑wattage space heaters and portable A/Cs should go directly into a wall outlet.
• Unplug safely: Pull from the plug body, not the cord. Store loosely coiled; avoid tight knots.
• Label your cord: A small tag noting gauge and length saves time later.

Common Mistakes to Avoid

• Using an indoor cord outside or in damp locations
• Undersizing the gauge for the tool, causing overheating or poor performance
• Running under rugs or tightly coiling during use, which traps heat
• Daisy‑chaining cords or cords into power strips without checking total load
• Defeating the ground by removing the third prong or using a cheater adapter
• Permanent use as fixed wiring (not allowed by electrical codes)
• Backfeeding a home from a generator through a household receptacle (dangerous and illegal)

Related Terms

• AWG (American Wire Gauge): Wire thickness scale; lower number = thicker wire.
• Amperage (Amps): The amount of electrical current a device draws.
• Wattage (Watts): Power used; Watts = Volts × Amps.
• Voltage drop: Reduction in voltage over distance; worsens with long, thin cords.
• GFCI: Device that quickly cuts power on ground faults; protects people from shock.
• Power strip vs. surge protector: A power strip adds outlets; a surge protector also absorbs voltage spikes. Neither increases circuit capacity.

Practical Examples

• Mowing the lawn with a corded mower: Choose a 12 AWG, outdoor‑rated SJTW cord in a length that covers your yard without excess slack. Keep the cord behind you, and use a GFCI outlet.
• Using a circular saw in the driveway: A 14 AWG outdoor cord is often fine for short runs. If the saw bogs down or the cord warms noticeably, move to 12 AWG or shorten the cord.
• Holiday lights along the eaves: Use an outdoor‑rated cord and weather‑resistant cord clips. Keep connections off the ground and covered from direct rain. Don’t overload the cord—add up the light strings’ total watts.
• Basement dehumidifier during remodel: If you must extend temporarily, use a short, 14 or 12 AWG grounded cord, and plan a dedicated outlet as a permanent fix.
• Generator hookup during an outage: Use a generator‑rated cord to a transfer switch or inlet box installed by a pro. Never run a cord from the generator to a household receptacle.

With the right gauge, length, and rating, an extension cord can safely bring power where you need it for short‑term tasks. Choose carefully, use it safely, and put it away after the job.