How to Determine the Load Capacity of Your Circuit Breaker

Understanding Circuit Breakers

Circuit breakers in your electrical panel are considered "Safety buffers." Their job is to disconnect from power when they detect the passing current exceeds its amperage. When you don't measure your circuit breaker's load capacity, you run the risk of damaging your appliances, or worse…setting your building on fire! In this blog, we will go over the key essentials to understanding how much amperage your circuit can hold.

Key Essentials:

Circuit Panel

When you’re considering installing a new heater, HVAC unit, thermostat, or any electrical appliance for that matter, it’s important to know exactly how much electricity your circuit breakers can handle before the circuit trips.

Every electrical appliance you use requires a specific level of electrical power for it to operate safely.  Commonly referred to as the “Power Rating,” this load level helps to determine how much power your device can handle without overheating (8).

Have you ever gone shopping for batteries, light bulbs, or even vacuum cleaners and noticed things like ‘9-volt batteries’ or ’12-watt light bulbs’ or ‘20 amps of power?'  Have you ever looked at these numbers and found yourself asking…

WATT does it all mean?

Well, before we jump into load capacity and all that other technical jargon, let’s learn a little bit about amps, watts, and volts.

What is an amp?

Amp is short for Ampere.  Amps measure the amount of electrical charge flowing past a given point in one second. In laymen’s terms, the number of amps indicates how much of an electrical current is being drawn through power cables (1).

What is a volt?

Voltage (volts, V) measures how strongly electricity is being pushed through a circuit. In other words, the number of volts tells you the amount of pressure being pushed (1).

What is a watt?

Wattage measures the amount of electrical power that a device uses.  Watts is the unit of measure that indicates the total amount of electrical current flowing through an electrical device (1). By measuring the amount of power a building consumes, the power company is able to determine your utility bill.


Still don’t get it? Let’s use a water hose as an example!

Like electricity running through a current, water flows through a hose. Amps would be the volume of water that flows through the hose, while the actual water pressure would be the voltage (1). Watts on the other hand is directly related to the power that water could provide. For example, it could be powering a water wheel.

How to evaluate your electrical load capacity

Every circuit breaker has a specified amperage (amount of current). This rating is labeled on the breaker itself.  The standard for most household circuits are rated either 15 amps or 20 amps. An important note to remember is that circuit breakers can only handle about 80% of their overall amperage.  That means a 15-amp circuit breaker can handle around 12-amps and a 20-amp circuit breaker can handle about 16 amps.


  1. First, find the breaker that correlates to the electrical device you are using (This is normally either a 15-amp or 20-amp circuit).
  2. Multiply the amperage by 0.8. This is because a circuit breaker should never exceed 80% of its max amperage. Not doing this could leave room for calculation errors, or even worse – electrical fires!
  3. Calculate the amperage draw of ALL the devices you wish to plug into the circuit.

Determining the number of electrical devices your breaker can handle

It’s very important to understand how much amperage your electrical device draws before installing them into your breaker box. Whether you’re looking to install a heater, AC unit, light switch, or GFCI outlet, there are a few steps you must take.


  1. Check the wattage (max power rating) on your device. This is usually labeled somewhere on the back of the device.
  2. Measure the voltage on the circuit you wish to install your electrical devices. Most household circuits are 120V and larger commercial spaces are 240V (5). If you’re not sure, use a multimeter to test the voltage of your breaker (5).
  3. To calculate amperage, use the equation Amps = Watts/Volts. For example, a 200W light bulb on a 120V circuit would draw about 1.67 amps.
  4. Calculate the TOTAL amperage rating of all devices. Make sure they DO NOT exceed 80% of the breaker’s total amperage.

Troubleshooting and inspecting your breaker panel

Your circuit breaker is an essential part in the safety of your home or building. It keeps your electrical wiring system from overheating. If you are experiencing frequent power outages, electrical trips, and other oddities, we’ve got some troubleshooting tips for you!

What are some common reasons for a circuit breaker to trip?

  1. Overloading the circuit with too many appliances that draw too much amperage
  2. Short in the electrical wiring, loose wiring, or wiring
  3. Circuit breaker is old, worn out, or damaged

These are just a few ways to troubleshoot a tripped breaker. Depending on the problem, some issues can be tackled at home while others will need the help of a qualified electrician.

Now that you have a little background knowledge on circuit breakers and how to troubleshoot trips, take your new skills and check out HomElectrical’s wide array of LED lights and HVAC units for your convenience.


Recommended Reading

Electrical trips can occur due to worn out insulation, conductive dust or debris, water, or electrical wiring deterioration. Discover more ways to troubleshoot your GFCI if it starts to trip.

Circuits and outlets come in either 15-amp or 20-amp options, and the amperage of the outlet must never exceed the amperage of the circuit. Follow NEC requirements to make sure you have the correct voltage, and never overload your circuits.

GFCI breakers and receptacles keep you safe from electric shocks and fires. Use a GFCI outlet in areas with a high chance of water coming into contact with the electrical current, such as a bathroom or kitchen.

GFCI stands for Ground Fault Circuit Interrupter outlets, while GFI stands for Ground Fault Interrupter. Many electricians refer to GFCI instead of GFI, but neither word signifies a difference.

Shakir Williams
Shakir Williams

A true creative with a penchant for the spiritual and natural order. She loves the Earth, almost as much as she loves writing about it.

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