How Many Outlets Can Be Placed on a 20 Amp Household Circuit?
The circuit breakers in the electrical panel in your house are safety devices. Each one is designed to disconnect power when the current passing through the circuit exceeds its rating. This prevents overheated wires, electrical power surges and fires. Electrical outlets don't draw power until you plug something in, so a 20-amp circuit should theoretically be able to handle as many outlets as you want without overloading the breaker. There are practical limits, though.
Allowable Breaker Load
The National Electrical Code doesn't limit the number of receptacles you can place on a 20-amp circuit, but you'll overload the breaker if you run appliances that draw more current than the breaker can handle. The NEC does specify that a circuit breaker shouldn't handle more than 80 percent of the load for which it is rated unless the breaker is labeled otherwise. By this standard, the total current draw on a 20-amp circuit shouldn't exceed 16 amps. This allows the breaker to handle the temporary surge that happens when an appliance such as a power saw or air conditioner starts up.
When deciding how many receptacles to add to a 20-amp circuit, consider what you are likely to plug into each one. For safety, the total draw on the circuit shouldn't exceed 16 amps at any one time, which translates to a maximum power draw of 1,920 watts on a conventional 120-volt circuit, even though the breaker won't trip until the power draw exceeds 2,400 watts. You should limit the number of receptacles on a circuit that will handle a power-hungry appliance. For example, most electric heaters draw 1,500 watts, so a circuit that powers one should have few other receptacles.
Spreading the Load
To better distribute the power consumption among all the breakers in the panel, combine lights and electrical outlets on a single circuit, because lights typically draw less power than appliances. Your kitchen must have at least two outlets, each on separate circuits, so that if one breaker trips, you still have power. Adding lights to each circuit balances the load and avoids the necessity for separate lighting circuits. Certain kitchen appliances, however, such as the dishwasher, must be on a dedicated circuit, which means that you can't include anything else on the circuit -- not even lights.
In most circuits, only one outlet is likely to be in use at any one time, so it's a good strategy to spread as many as possible around the house on a single circuit to guarantee you have power where you need it. One rule of thumb is to assign a maximum draw of 1.5 amps to each receptacle, which allows for 10 receptacles on a 20-amp circuit. You must use 12-gauge wire to connect 20-amp circuits; when you're installing receptacles in the bathroom, kitchen, laundry room or outdoors, they must generally be ground fault interrupting receptacles.
Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.