What Size Extension Cord Do I Need for Common Appliances?

Start with the appliance label

Every appliance has a label, often called a nameplate, that lists its power draw in watts or amps. Look on the back, the bottom or near the cord. If it lists only amps, multiply amps by volts to get watts. A standard US outlet is 125 V, so a 10 A appliance draws about 1250 W.

The cord you buy must be rated for at least that much. Cord ratings on our spec sheets follow the same math: 15 A at 125 V is 1875 W, and 13 A at 125 V is 1625 W. If your appliance is close to the limit, step up to the next heavier cord instead of squeezing by.

How gauge, amps and length work together

Wire gauge is listed as AWG, and a lower number means thicker wire. Thicker wire carries more current with less heat and less power lost along the way. Length matters because a longer run adds resistance, so the same cord handles a load less well at 100 ft than at 25 ft.

Here are the ratings on the cords we compare, so you can see how gauge and length line up with amps and watts.

• Thicker wire (12 AWG) suits heavier loads and longer runs.
• Thinner wire (16 AWG) suits lamps, chargers, fans and other light loads over short distances.
• Buy the length you need, not extra. Extra length adds loss without adding value.

Quick guide for common appliances

Exact wattage varies by model, so always confirm on the label. These are general guidelines for matching a cord to the type of load.

For small items such as lamps, phone chargers, a box fan or a radio, a light 16 AWG cord is usually enough over a short distance. Our 6 ft indoor cord and 25 ft outdoor cord both list 13 A and 1625 W, which covers light loads that stay under that limit.

For power tools, string lights, hedge trimmers and lawn equipment, lean toward 12 AWG. Tools that start with a surge, such as saws, ask more of a cord than their running watts suggest. A 12 AWG cord with 15 A and 1875 W ratings gives you more headroom.

For space heaters and other heating appliances, be especially careful. They draw a steady, high load for hours, which makes cords warm. Plug them straight into a wall outlet when you can. If you must use a cord, use a heavy one that is rated well above the heater's draw, and feel the plug and cord now and then for warmth.

Air conditioners, generators and pool pumps

Air conditioners: Many manufacturers tell you to plug a window or portable unit directly into a wall outlet, because compressors draw a lot at startup. Read the manual first. If a cord is allowed, it should be short, heavy gauge and rated above the unit's amps. Never use a thin cord or a power strip.

Generators: Check the generator's outlet type and amp rating. A cord that fits a standard 15 A outlet will not fit larger locking outlets, so you may need a generator-specific cord. Use a heavy gauge cord sized to the load you are running, and keep the run as short as practical. Always run a generator outdoors, well away from doors, windows and vents, because the exhaust contains carbon monoxide.

Pool pumps: Many pool pumps are hardwired or run on a dedicated circuit, and some need 240 V. A standard 125 V cord is the wrong tool for those. If your pump has a plug and the manual allows a cord, use an outdoor-rated 12 AWG cord, keep plug connections off wet ground, and plug into a GFCI-protected outlet. When in doubt, ask a licensed electrician to add a proper outlet instead of relying on a cord.

Choosing for 15 amp and 20 amp loads

For a 15 A load, a 12 AWG cord rated 15 A and 1875 W is the matching size. As a habit, keep steady loads comfortably below the cord's maximum instead of right at it. Our best extension cord page lists three 12 AWG cords at 25, 50 and 100 ft, so you can pick by reach.

For a 20 A load, check the plug shape first. The cords on our page list a NEMA 5-15 plug, and their maximum is 15 A. A 20 A appliance generally needs a cord built and rated for that current, which is a different product from the cords we compare. Do not force a 15 A cord onto a 20 A job.

Indoor or outdoor, and a few safety rules

Match the cord to where it will live. Indoor-only cords, like our 6 ft Amazon Basics model, lack weather protection. For lawns, patios and job sites, choose a cord with an outdoor or waterproof rating. Several of the cords we compare list a jacket that stays flexible down to -58°F, which helps in winter. Look for a lab mark such as ETL/cETL, which appears on six of the seven cords on our page.

Storage matters too. Reeling cords neatly protects the jacket and plugs, and our best extension cord reel page is a good place to compare options. Even so, fully unwind a cord before heavy use, because a coiled cord traps heat.

• Do not daisy chain cords or plug one power strip into another.
• Stop using any cord with cracked insulation, bent prongs or a warm plug.
• Keep plug connections out of puddles and off wet ground.
• Never remove the grounding pin to fit a two-prong outlet.
• Use a GFCI-protected outlet outdoors.

A simple way to choose in three steps

Follow this short routine each time you shop.

• Find the appliance's watts or amps on its label.
• Pick a cord whose watts and amps are higher, using 125 V as the standard.
• Choose the shortest length that reaches, and the thickest gauge your load calls for.

Frequently asked questions

Can I use a thinner cord for a short distance?

Sometimes. A short run loses less power, so a lighter cord can work for small loads. It still must be rated for the appliance's amps and watts.

Does a longer cord need thicker wire?

Generally yes. Longer runs add resistance and heat, so a heavier gauge helps a load run well at 50 or 100 ft.

Is it safe to leave an extension cord plugged in all the time?

Extension cords are meant for temporary use. For a device that needs power permanently, an added outlet installed by an electrician is safer.

What does the lighted end do?

It is an LED that shows the cord is receiving power, which helps you spot a tripped breaker or a dead outlet.