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What Size Breaker for a Hot Water Heater? Get the Facts Here

Fact checked by Stephen Conklin

What Size Breaker for a Hot Water Heater

Are you confused about what size of circuit breaker you need to buy for your electric water heater? Do not fret because you are not alone.

Determining what size breaker for a hot water heater is crucial for ensuring your water heater’s efficient operation and your family’s safety.

Circuit breakers protect your home’s electrical circuit against short circuits, overloading, and overcurrent by interrupting electric current flow when it detects a fault. In essence, it also protects your water heater. That is why you need to choose the right size of circuit breaker to use with your water heater.

Size Breaker for Hot Water Heater


Circuit breakers for electric water heaters can have a rating as low as 15 amperes and as high as 100 amperes. Unfortunately, there are no hard and fast rules to determining the circuit breaker size appropriate to your water heater.

In general, an electric water heater should have a dedicated 240-volt circuit without any device or appliance connected to the same circuit. This 240-volt circuit serving the water heater should also have a 30-amp double-pole circuit breaker.

If your water heater connects to a 120-volt system, a 20-ampere single-pole breaker will suffice. However, you should also look at the heating elements’ wattage rating. For instance, a 2500-watt heating element will work best with a 30-ampere circuit breaker.

Determining the Size of Hot Water Heater Circuit Breaker


No two electrical systems are alike, as no two water heater systems are 100% identical. Different households have their unique electrical system. Determining what size of circuit breaker you should get for your water heater involves an easy four-step process.

Check Your Electric Water Heater’s Power Rating

All electric appliances and devices have a power rating, expressed in watts. Knowing your water heater’s wattage rating is the crucial first step to determining the size of the circuit breaker you will need.

Check your water heater’s specifications label located on the unit housing next to the power cord. You should see the number of watts your water heater has. Most electric water heaters have 1,500 watts of power. Commercial-grade units may have heating elements with a power rating of up to 5,500 watts.

If you cannot find your water heater’s power rating, you can try computing for it. The US Department of Energy recommends looking for the amperage rating and multiplying this by your system voltage. Most American appliances run on 120 volts, except for large appliances that use 220 volts.

For example, if your water heater says it uses 12.5 amperes, you can multiply this by 120 volts to get 1,500 watts.

Determine your Water Heater’s Maximum Current Draw

Your water heater’s power rating is one thing. Knowing how much electricity it uses during operation is another matter. That is why you also need to calculate its maximum current draw in amperes. Your water heater’s amperage rating translates to the amount of electricity it needs to operate optimally.

Most products already provide this information on their specifications label. If you do not see it, you will have to divide your water heater’s power rating by its operating voltage.

For instance, an electric water heater with 1,500 watts running on 120 volts will have a maximum current draw of 12.5 amperes (1,500 divided by 120 = 12.5).

Assess Your Circuit Breaker’s Electric Current Rating

You might think that a 12.5-ampere circuit breaker is sufficient for a 1500-watt, 120-volt water heater, looking at our computation above. That is not the case. You need to multiply your heater’s maximum current draw by 125 percent or a factor of 1.25.

With this formula, you will need a circuit breaker with an amperage rating of 15.625 amperes (12.5 amperes x 1.25 = 15.625 amperes).

Pick the Correct Size of Circuit Breaker for Your Electric Water Heater

It would be more appropriate to get a 20-ampere circuit breaker than a 15.6-ampere unit, referring to our computation above. Getting a breaker with the next higher amperage rating minimizes overloading your system and saves you from electrical accidents.

Ideally, you want a circuit breaker that can accommodate your water heater’s power draw without exceeding 80 percent of the breaker’s capacity.

Suppose you have a 20-ampere water heater operating on a 120-volt system. You may think getting a 20-ampere circuit breaker is a good idea. However, your water heater’s current draw is already 100% of the breaker’s capacity. You will need a 25-ampere circuit breaker for this set-up.

Twenty amperes is 80% the capacity of the 25-ampere circuit breaker. It stabilizes your circuit and allows your water heater to work consistently and efficiently, too.

Does Wire Gauge Have an Impact on the Choice of Circuit Breaker

It is essential to understand that a wire gauge impacts the size of the circuit breaker you choose. Wire gauge determines the amount of electricity that it can carry without overloading or damaging your system.

The wire gauge is inversely proportional to the conductor’s diameter. As such, the greater the wire gauge number, the smaller is the conductor’s diameter. For example, a 10-Gauge wire has a cross-sectional area of 5.26 square millimeters and a diameter of 0.1019 inches.

You can learn more about wire gauge sizes here.

If you chose a 30-ampere circuit breaker for your water heater, the minimum wire gauge for your 120-volt system is 10-Gauge. You can also install 8-Gauge wiring for a 30-ampere circuit breaker serving a 3000-watt, 120-volt water heater.

Here is a helpful table for finding out the circuit breaker sizes and wire gauges for different wattage-rated and voltage-rated water heaters.


Learning how to determine what size breaker for a hot water heater involves an easy four-step process. It includes knowing your water heater’s power rating, its maximum current draw, and its corresponding circuit breaker amperage rating.

The value you come up with can tell you the circuit breaker’s ideal size to use with your water heater. It can safeguard your electrical system, the water heater, and your family’s well-being.

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