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What Size Electrical Wire Do I Need?

Wire Gauge and Ampacity

By , About.com Guide

An image of electrical wire lettering.

Electrical Wire Lettering

Timothy Thiele

In order to install any electrical wire installation, the proper wire size for the application is needed. But how do you know what size wire to use? Wire is sized by the American Wire Gauge (AWG) system. Your installation of conductors will depend on a few factors. The gauge of the wire, wire capacity, and what the wire will feed should all be considered.

You’ll notice that the smaller the wire gauge, the larger the ampacity that the wire can handle. Wire ampacity is the safe amount of current that a wire can handle without getting hot or causing a fire. The following examples of devices in your home, the ampacity that they are rated for, and the wire gauge, will help you determine the right size wire for the appropriate application.

Wire Gauges and Uses

Wire UseRated AmpacityWire Gauge
Low-voltage Lighting and Lamp Cords10 Amps18 Gauge
Extension Cords13 Amps 16 Gauge
Light Fixtures, Lamps, Lighting Runs15 Amps14 Gauge
Receptacles, 110-volt Air Conditioners, Sump Pumps, Kitchen Appliances20 Amps12 Gauge
Electric Clothes Dryers, 220-volt Window Air Conditioners, Built-in Ovens, Electric Water Heaters30 Amps10 Gauge
Cook Tops45 Amps8 Gauge
Electric Furnaces, Large Electric Heaters60 Amps6 Gauge
Electric Furnaces, Large Electric Water Heaters, Sub Panels80 Amps4 Gauge
Service Panels, Sub Panels100 Amps2 Gauge
Service Entrance150 Amps1/0 Gauge
Service Entrance200 Amps2/0 Gauge

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