The correct wire size for a 20 amp breaker is 12 AWG copper wire. It is rated 20 Amps at 75°C.

 Note that a 14 gauge wire on a 20 amp circuit is not the correct size, as it is only rated to handle up to 15 Amp in residential applications. Using 14 AWG for a 20 Amp breaker will result in overheating and a risk of electrical fire.

Using a 10 AWG wire for a 20 amp circuit is possible and safe but not cost-effective. However, this might present some issues. For example, the larger wire may not fit the terminals on certain devices or fixtures rated for 20 amps.

Aluminum wire is not a popular choice for a 20 Amp breaker, and it is usually replaced with a copper wire. However, the size of an aluminum wire for a 20 Amp circuit is the same - 12 AWG.

All things concerned, 12 AWG copper wire is the perfect 20 amp wire.

What Are The Applications Of A 20 Amp Circuit?

Like 15-amp circuits, 20-Amp circuits can be either dedicated or shared.

A 20-amp circuit at 120 volts can deliver up to 2,400 watts of power. According to the NEC rule, a circuit should only be used 80% of its maximum capacity for continuous loads. This means only using approximately 1,920 watts on a 120-volt circuit at once for 3 hours.

A 20-amp outlet has one slot turned sideways or T-shaped to accept 20-amp plugs.

A 20-amp circuit is used for different heavy-duty kitchen appliances. These include:

• Kitchen circuits (dishwasher, garbage disposal, microwaves, toasters, blenders).
• Laundry circuits like washing machines. Electric dryers need 240V.
• Bathroom circuits, including appliances like curling irons and hair dryers.
• Personal office rooms, with devices like computers and printers.
• Garages that have power tools and car repair equipment.
• Air conditioners that are either large window units or central units on a smaller side.

So, which of the appliances requires a dedicated 20 Amp circuit?

These are refrigerators, dishwashers, microwaves, washing machines, electric heaters, garbage disposals, and air conditioners. The need for a dedicated circuit is a result of a large power demand.

Cables For 20 Amp Circuits 

• NM-B Non-Metallic Sheathed Romex® Cable is the most popular cable for indoor 20-amp circuits. It is recommended for all kinds of strictly interior wiring when the cable is not impacted by moisture and does not need extra protection. Laundry, kitchen, and bathroom circuits also mostly use NM-B, as long as the cable is kept away from the water source.
• THHN/THWN in both copper and aluminum in conduit. It is often used when wiring is exposed or requires additional protection, like in garages.
• UF-B cables for circuit breakers located outdoors, such as air conditioners partly located outdoors and garages. Not used in interior applications, except for direct exposure to moisture, such as under sinks.