Understanding your home’s electrical system could be at the bottom of your priority list, but there are times when it’s useful to understand what some of its jargon refers to, like the numbers in this title. They describe the maximum amount of electricity that can go through a circuit without making it shut off or trip.

The wires coming into your home from the main meter separate into different sections. How many you have and what their amps are depends on how large your home is and how much power you need. A home that uses all electric appliances will need more circuit breakers that have a higher amp rating than one that uses gas appliances.

Finding Power Ratings

Everything that uses electricity indicates somewhere on it or the packaging how much power it uses, whether it’s in volts, kilowatts (kW), or amps. Each of these gives you an idea of how much the appliance or device it uses. Generally, only high-usage appliances like air conditioning systems, electric water heaters, stoves, dryers and heaters indicate their amp use. Light bulbs and televisions indicate their use in watts.

You might find volts as a rating on some devices, along with kilowatts. Between the two, you can find how many amps they have by multiplying amps times volts and dividing by 1,000 to get to watts,

Why It Matters

When you’re using electricity, you have to be careful not to use too much coming from one wire. Overloaded wires can easily start fires, which is why all electrical lines go through a circuit breaker box before going to an outlet or a switch. The numeric designations, i.e. 10, 15, 20, 110 and 220 indicate how many amps the wire can handle.

For example, a central air conditioner for an average-sized home may use 20 amps of electricity to run. If its wiring goes through a 20-amp circuit, you won’t be able to use any other electric device on that circuit, even if it’s a 10-watt light bulb. The circuit breaker will heat up because it’s overloaded, and will shut itself off, turning off the power to the air conditioner.

The circuits designated for the switches and outlets are usually 10- and 20-amp circuits. Even though lights and small appliances don’t take much electricity, they can add up if you’re using too many devices on one circuit. Running a vacuum cleaner, a microwave and a coffee maker is likely to trip the circuit, since each of these uses more kilowatts (aka amps) than light bulbs do. Computer use adds up on a circuit, as do irons, toasters and large screen TVs.

Bottom Line

Knowing how much power each circuit is capable of providing will help you avoid tripped circuit breakers. It’s also useful when you’re planning rooms where electricity use can be high, like kitchens, garages and laundry rooms.