A power panel can have 40 or more circuit breakers, depending on its size and use. Each breaker is sized at 80 percent of the maximum allowable current for that size of wire. This is a rule required by the National Electric Code, which provides a buffer zone to help reduce the number of fires caused by overloaded cable.
15-amp Circuit Breakers
A 15-amp breaker is used for lighting fixtures and and regular-duty receptacles. They allow a maximum of 1800 watts of power on one branch circuit. These are the circuits most common in homes and can be found in living rooms, bedrooms, hallways, etc.
20-amp Circuit Breakers
A 20-amp circuit breaker is used mostly in the kitchen, garage, businesses and for small heating applications. These breakers allow a maximum of 2400 watts on a branch circuit. They supply power to appliances such as freezers, refrigerators, dishwashers and various power tools, such as circular saws. In businesses, these breakers are standard. Most businesses do not use 15-amp circuits.
30-amp Circuit Breakers
A 30-amp circuit breaker is used mostly for clothes dryers. These breakers are usually double breakers, because they are typically carrying 240 volts as opposed to 120 volts. These breakers allow a maximum of 7200 watts on a branch circuit.
40-amp Circuit Breakers
A 40-amp circuit breaker is usually used for heat pump units. This breaker can also be a single or double breaker. These breakers allow a maximum of 4800 or 9600 watts, depending on how the circuit is configured and the size of the heat pump.
50-amp Circuit Breakers
A 50-amp breaker is used mainly for stoves. Stoves require a large amount of current and voltage to operate. These breakers allow a maximum of 12000 watts on a stove circuit. Because of these high power needs, stoves are usually located as close to the main power panel as possible.
60- and 100-amp Circuit Breakers
A 60- or 100-amp breaker can be used to feed another power panel or a subpanel. A subpanel is a smaller version of a power panel used to add additional breaker slots, or it can be used as a service panel for a garage or workshop.