How to Prevent Circuit Overload

2018 Jun 12
Posted in:

Overloading a circuit is dangerous. When too much current runs through wiring that can’t support it, you risk overheated wires and eventually an electrical fire.

The good news? Every circuit has built-in protection (the circuit breaker) that prevents wires from getting overheated. A circuit breaker will automatically “trip” and cut power to the circuit when it senses a current overload.

The bad news? If a circuit breaker goes bad (and all of them eventually do), it will stop protecting you from these electrical fires.

That said, the safest way to protect your home is to prevent circuit overloads altogether.

Not sure how to do this? Just follow the steps below to prevent overloading your home’s circuits:

  1. Determine which appliances are on which circuits
  2. Calculate the current load on each circuit
  3. Determine the capacity of each circuit
  4. Plan according to the numbers above

We’ll explain each step below to ensure you never overload an electrical circuit again.


Have a circuit that’s constantly overloaded? You might need a new circuit installed or you may just need to replace a circuit breaker.

Whatever the electrical need, just contact us.



Step 1:  Determine which appliances are on which circuits

Every circuit has a limit to the wattage it can provide. Knowing how many (and what kind of) appliances live on a certain circuit will tell you how much of that circuit’s wattage is already being used up.

To start, locate your home’s electrical panel (usually located in a garage, storage closet or basement). Open the cover and turn off only one breaker at a time.

Important: Only flip breakers labeled with a “15” or “20”. There is no need to flip/turn off higher-rated breakers (30, 40, 50) as these are “dedicated” circuits that only ever send power to a single appliance.

Quick science lesson: the numbers on your circuit breaker (15, 20, 30, etc) refer to the circuit’s “amperes”—that is, how much electrical current the circuit has. Wattage (which we’ll discuss in step #2) refers to the strength of that current.

After you turn off a single breaker, walk around the house and determine which appliances no longer have power. Jot down these appliances on paper and group them according to their circuit breaker.

Once you’ve written down all the appliances on that circuit, go back to the electrical panel and turn the breaker back on. Then, repeat the process for each 15/20-amp breaker in your panel.


Step 2: Calculate the current load on each circuit

To complete this step, add up the wattage of every appliance living on a circuit.

The wattage should be listed somewhere on every appliance (see below for example).

appliance wattage

Wattage listed on the bottom of a toaster.



If a circuit has:

  • 1 toaster = 850 watts
  • 2 kitchen overhead lights = 64 watts in total
  • 2 lamps = 16 watts in total
  • A ceiling fan = 75 watts

Then the total wattage = 1,005 watts


Step 3: Determine the capacity of the circuit

A 15-amp circuit has a maximum wattage load of 1,800 watts and a 20-amp circuit has a maximum wattage load of 2,400 watts

But here’s the tricky part: For safety purposes, you should not exceed more than 80% of a circuit’s maximum wattage.

So, really, the safe capacity of your circuits are:

  • 15-amp circuits: 1,440 watts
  • 20-amp circuits: 1,920 watts


Step 4: Plan according to the capacity of each circuit

Compare the current wattage load for each circuit (from step 2) with the circuit’s capacity. If the current load is close to capacity, be sure not to add anymore appliances to that circuit.

To make this easier, label any outlets that live on full (or close to full) circuits. This will help you avoid any electrical overloads and/or tripped breakers.


Problems you may encounter after these steps

Problem #1: Circuit breakers are still tripping (but circuits aren’t at capacity)

If a circuit breaker continues to trip when the circuit isn’t at capacity, the problem is most likely bad wiring or a bad appliance.

You see, circuits breakers are also designed to trip if they sense a “short circuit” or “ground fault”. Both of these electrical problems are caused by faulty wiring that allow current to jump from one wire to another (this should never happen).

To learn more, check out our blog, "Why Does My Circuit Breaker Keep Tripping?”.

If you think you have a bad appliance, have a professional inspect the circuit to determine which device is faulty.

Problem #2: All your circuits are at (or close to) capacity

If you’ve done the math and noticed that all of your 15 and 20-amp circuits are close to 80% capacity, you may need to have a professional either:

  • Add a circuit to your panel
  • Upgrade your main electrical panel

Every panel has a limited amount of circuits it can provide to the home. Most homes today need at least a 100-amp main panel in order to power all of its electronics. So, if your home has less than a 100-amp service, you’ll likely need to upgrade your panel soon.

Related: What Size Electrical Panel Do I Need for My Arizona Home?


Have circuit overload questions? Ask our Arizona electricians

George Brazil offers fast electrical service and professional, licensed electricians you can trust.
Contact Us