Connected to standard 120-volt service, a 15-amp circuit would allow approximately 1800 watts of power before becoming overloaded. For long-term loads, including anything that draws current for more than three hours, the maximum wattage allowed would be 20 percent lower, at 1440 watts.
Going over the rated wattage on a circuit will increase the amperage to the point where the fuse or circuit breaker may trip, shutting off the power. If a circuit breaker repeatedly interrupts power to a 15-amp circuit, moving appliances to other circuits may lower the draw and prevent further interruptions. Running a circuit near its maximum capacity for a long period of time may lead the wires and circuit breaker to overheat, potentially causing damage to the connections.