What Is a 20-Amp Outlet? A 20-amp outlet is only compatible with a 20-amp circuit.The circuit's ampere rating can be found by checking the breaker box.A 20-amp outlet is identifiable by horizontal slots that cross the more typical vertical slots of a normal outlet.This kind of outlet is served by either 12-gauge or 10-gauge wiring. A 20 amp circuit breaker means a maximum of 20 amp (amperes) of current can flow through the circuit. 20 amp refers to the amp rating of the circuit.Amp or ampere is the unit of measurement for current.So, a maximum of 20 amp current can safely flow through a 20 amp rated circuit,or the circuit can handle a maximum load of 20-ampere current. A 20-amp circuit needs 12-gauge or bigger wire.A 15-amp circuit can use either 14-gauge or 16-gauge wire.The amperage of a circuit determines what size wire you need.If you have a circuit that uses more current than the maximum for its size,then you will get a hot spot and require larger cable.