“Norma – I’m going to be moving into a new apartment with semi old wiring. There are three walls each with several plug-in outlets on the same breaker. Plug too much stuff in and it overloads the breaker. Is the easy fix just giving some of those outlets their own breaker or is it a larger issue?” – WYSK Reader Katieloe

NV: Hi Katieloe, Thanks for posting this breaker overload question – it’s something everyone can relate to, especially if they’re living in an older home without an upgraded electric service.

To be clear, I’m assuming when you say “overloads the breaker,” you mean a response to many things being plugged in (and running at the same time) that can range from dimming lights to actually tripping the breaker. If this is what you mean, indeed, it sounds like the circuit is being overloaded.

To really understand the question at hand, let me give you a little Amperage 101 lesson. Receptacles that serviced homes built several decades ago fall short given the amount of electronics, appliances, etc. we use today. One outlet in a medium sized room sufficed back then. Today, the standard is one receptacle every six feet! While an older home may have only a 100amp service, today the same size home will have a 200amp service or more.

As for amperage, most circuit breakers in your service will be 15amp. Generally speaking, on a 15amp breaker, conservatively, you can use 80% of its amperage all at once, which is 12amps. This means, no matter which outlets you’re using in one particular circuit, or how many things you have plugged in to it, the total amperage load should not exceed 12amps.

The question now becomes, how am I supposed to know how many amps I’m pulling? There’s a formula – Watts/Volts=Amps – and once you know what numbers to plug in, it’s easy to figure out.

For example, if you’re using a 1200watt microwave on a typical 120volt line, it will pull 10amps (1200w/120v=10amps)… leaving you with only 2amps on that circuit (remember, max usage on a 15amp breaker is 12amps). So let’s say while you’re heating up your Hungry-Man Fried Chicken Dinner, on the same circuit, someone starts up their brand new 1300watt Turbo Ionic Hair Dryer… POP, that breaker is definitely going to trip! (1300w/120v=10.83amp, a total of 20.83amp!)

The truth is, it doesn’t matter if you have 2 or 200 outlets on one circuit (to exaggerate a point), it will only overload if you’re using more amps than what that particular circuit breaker is designed to handle.