For standard 120-volt service, a 20-amp breaker can support up to 2,400 watts on a single circuit. However, circuits should not be loaded to greater than 80 percent of their maximum capacity for long periods, which makes 1,920 watts the safe maximum for a 20-amp circuit.
Running a circuit near its maximum capacity for long periods can cause the wiring and connections to become warm and may trip the circuit breaker. If a breaker trips repeatedly, appliances should be moved to other circuits to reduce the load on the affected circuit. Constant overloading can lead to damage and increase the risk of fire.