By Erik Watkins

What Size Breaker For Water Heater

Last updated: Jan 5, 2023
What Size Breaker For Water Heater

A size breaker is called a circuit breaker. They play a vital role in balancing safety checks for any electrical circuit. Therefore, improper usage could lead to a series of fairly terrible consequences. The following article will help you find the solution to “what is water heater breaker size?”

About Water Heater

Before fully knowing the size of a water heater, we should have a profound insight into the water heater, thus assessing its accompanying functions. These are pivotal fixtures in every home. That’s why you feel water is cold or warm, depending on the temperature. To get the water warm enough to take a shower or wash dishes, you must have a device that changes the temperature of the water.

This article would focus on the domestic kind so that everyone could raise their awareness about their safety. Regarding its frame, there are three major controls on the left at the bottom, and the first one, which lies on the far left, plays an important role in heating and generating a hot water heater breaker. It is also the main control switch. Please ensure it’s in the “on” mode when using. You also can check it on the water heater breaker size chart.

The Formula Of Breaker Size

If you waver about the correct breaker size, you should consider a series of factors to ensure your safety, such as voltage, wattage, and wire size. You should also have clues about the amp size by an uncomplicated calculation.

Do not worry too much about the complexity because you must follow one rule called the Ampere formula illustrated scientifically. It is I (amps) = P (watts) / V (volts). If you are clueless about this formula, we suggest a simple example so that you can base it on this to adopt practically.

For instance, you have a tank of nearly 3,000 watts heater that needs 120-volt power. You have to split your watts by volts. As a result, I=3,000 watts / 120 volts = 25 amps. It is a common mistake that this device needs a breaker size with the same utility. This mistake could lead to overloading. 

According to regulation by NEC or the National Electric Code, 125% of the high sampling load would be the best choice. We can calculate quickly and obtain the nearest amp size, approximately 35 amps. 

Your heater will certainly trip if you own a 20-amps breaker and a 25-amp water heater. But make sure that you will make room for your breaker when it has a surge in power.

If you still can not make sense of these points, you could consult a series of prestigious websites, such as Youtube and Linkedin, to better understand that sizing your heater and breaker size is proper. 

How Is The Water Heated?

Although these types of equipment are familiar fixtures in most homes, many people have little understanding of this, thus encountering a series of dangerous accidents. Refrain from letting the simple shape fool you. Its structure could surprise you despite the simple outside look.

Let’s quickly look at what’s happening inside a heater’s tank. Its thermostat controls the temperature. After being heated enough, water exits through the heat-out pipe near the top of the tank. An interesting fact about this device is its design which separates incoming water from outgoing water. The tank will fill up as time passes, and you can use hot water.

The Way To Examine The Correct Size Breaker For Your Home

Correct Size Breaker

Step 1

It is never a good idea to build a specific volume breaker to be too large or too small to cover many features in your house. Therefore, before finding a suitable one capable of handling electrical demand, you should do some research. Considering the water heater’s wattage and voltage specifications would be best.

Do not worry too much because you can typically detect these on the label marked on the thermostat’s control panel tank. If you still can not find any label information, you can base it on the manufacturer’s name and model number illustrated clearly on the water heater. The next step you need to do is to search on Google so that you can acknowledge a lot of facts.

Step 2

It is an essential step account that you can find a suitable size for your water heater. You can determine the proper breaker size by calculating the referred formula, Amps = Watts / Volts.

You could swipe up and look through part 2, “The formula of breaker size,” to gain more helpful information.

Step 3

After a quick calculation to calculate the max Amps your water heater required, you should consider the breaker size for your water heater. You could make the final decision by multiplying the Amps by 125% based on NEC Code

One more example may help you clarify more. If your device owns a 4500-wattage and 240-voltage rating, you reach the result through the formula, which is 18.75 Amps.

In the next step, multiply 18.75 Amps by 125%. The final result is approximately 23.43 Amps.

A 25- or 30-amp breaker for a water heater would be your best choice for a 4500-watt with 240-volt water heater.


How Do I Know The Size Breaker I Need?

As the below writing refers, you need to follow the instructions. The amperage of each circuit breaker should be indicated on the handle. This is the maximum amperage that the circuit can handle before tripping the circuit breaker. You could also hire a reliable mechanic to make adjustments in case you are unsure.

How Many Times Can The Circuit Breaker Be Turned On And Off?

It is reported that the typical hot water heater circuit breaker can last up to 10,000 operations. However, resetting it when all the faults appear is only sometimes good.

Can I Have One Circuit On The Two Breakers?

No. Two breakers can’t control the same circuit because of the high risks. This is dangerous because, even if done by mistake and the insulation was not damaged, two breakers together have a larger current rating than the wire in each circuit.


If you collect enough accurate information, you may select the suitable size breaker for your bathroom. All the shared ideas will help you make the best final decision for “what size breaker for a water heater?”. Hope that you could find this article helpful whenever you encounter any troubles related to the breaker for the water heater.

Automotive Mechanic at PowerAll

With 7 years experience in management positions leading automotive mechanics at PowerAll, Erik Watkins wishes to share useful knowledge and information about automotive mechanical equipment.


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