Household Electrical Wiring Sizes

Lighting Circuits

• Sheathed cable makes up most wiring in the United States, and 14-gauge is the most common size used. Standard lighting circuits rated at 15 amperes use 14-gauge copper wire. These circuits provide lighting for overhead fixtures and plug-in lamps. Most homes use this type of wiring, with the exception of kitchens, bathrooms, unfinished basements and garages. Lighting circuits connect to a 15-ampere circuit breaker.

Small Appliance Circuits

• Small appliances include refrigerators, microwaves, washing machines and hair dryers. Because these appliances use more electricity, they require larger wires. The wiring for small appliance circuits uses 12-gauge copper wire to carry up to 20 amperes of current and is protected by a 20-ampere circuit breaker. Some window or wall unit air conditioners use 240-volt wiring at less than 15 amperes. The circuits for these units may use 14-gauge wire instead of 12-gauge, but this is uncommon.

Large Appliance Circuits

• Large appliances include furnaces, electric ranges, clothes dryers, electric water heaters and central air conditioners. The wiring used for each appliance varies by the amount of electricity it uses. Common wire sizes for large appliances include 10-gauge, which safely carries 30 amperes; 8-gauge for 40 ampere appliances; and 6-gauge to carry 50 amperes. These large appliances utilize 240-volt, or 120/240-volt wiring. For example, a furnace may require less than 20 amperes for its blower unit and therefore uses a 12-gauge wire.

Aluminum Wire

• Aluminum wire is still allowed for new installation, but special restrictions apply. Most new homes have at least some aluminum wiring at the service entrance, where electricity is brought into the home. Aluminum does not carry electricity as effectively as copper, and larger gauge wires are required for each circuit. As a general rule, circuits wired with aluminum wire must use one larger gauge wire than you would for copper wire for the same circuit. Therefore, a 15-ampere lighting circuit uses 12-gauge aluminum wire, while a 50-ampere electric range circuit uses 4-gauge aluminum wire.