What Size Breaker Do I Need For My Water Heater?

What Size Breaker For Water Heater

Having the correct size circuit breaker for your water heater is critical to avoid serious issues. These issues can range from aggravating, like a constantly tripping breaker, to severe, like overheated wires and potential fires. The heating element wattage and operating voltage determine the size circuit breaker needed for your water heater.

Most residential water heaters have a 4,500-watt heating element, requiring a 240-volt dedicated circuit. Accounting for water heaters running continuously and using two heating elements, you need a 25 to 30-amp double-pole circuit breaker. The National Electrical Code (NEC) also recommends using a 10/2 non-metallic cable.

Of course, water heaters come in various capacities, featuring heating elements with wattage ratings less and greater than 4,500. For this reason, there’s a formula you can use to determine the correct size circuit breaker for your water heater.

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How To Determine The Circuit Breaker Size For A Water Heater

Water heaters feature a power rating, in watts, that dictates how much power it uses to run. In order to adequately push electricity through the cables, water heaters typically need to run on a 240-volt circuit. 

If you are unsure of your water heater’s wattage rating and operating voltage, check the label. You can find the label on the body of your water heater. It should contain this information, but you can check your appliance manual or the manufacturer’s website if it doesn’t.

You will need the wattage rating and the operating voltage to determine the correct size circuit breaker for your water heater.

Formula For Determining The Correct Circuit Breaker For A Water Heater

To determine the maximum current your water heater can handle, there’s a special formula you can use. Divide the power rating/wattage by the operating voltage. For example, for a 4,500-watt heater, you would divide 4,500 by 240.

The result is 18.75 amperes, but you’re not done yet. According to the NEC, electricians must follow the 80% rule, allowing circuit breakers 20% breathing room. This means that a circuit breaker should only handle a maximum of 80% of its electrical rating.

This wiggle room helps offset the amount of heat in the circuit for a minimum of three hours. However, with appliances that run 24/7, like a water heater, replacing the 80% with 125% is recommended.

Therefore, in the above example, you would then take 18.75 amperes and multiply it by 1.25. Your final number is 23.43, and rounding up, you get 25.

Therefore, you could use a 25-amp breaker for your water heater, but 30-amp breakers are more common. Using a larger amp can help prevent tripping the breaker, especially if you use a lot of hot water.

Examples Of Circuit Breaker Sizes For Water Heaters With Different Power Ratings

Using the above formula, you can ascertain the best size circuit breaker for various water heaters. Also, some smaller water heaters with power ratings of less than 3,000 watts might only need a single circuit.

These smaller water heaters typically only feature a single heating element, where larger heaters usually have two. So, if you have a small household with minimal hot water needs, you could potentially use a smaller water heater. Then, you could run it on a 120-volt circuit, adjusting the formula as necessary to swap out 240 with 120.

Here are some common examples of circuit breakers for different water heaters:

Power Rating of Water Heater Circuit Breaker Size
1,000 Watts (run on a 120-Volt circuit) 15 to 20-amp
1,500 Watts (run on a 120-Volt circuit) 15 to 20-amp
3,000 Watts (run on a 240-volt circuit) 20-amp
4,500 Watts (run on a 240-volt circuit) 25-amp to 30-amp (30-amp more common)
5,000 Watts 30-amp
5,500 Watts 30-amp

What Size Circuit Breaker For A 40-Gallon Water Heater?

Many 40-gallon water heaters have 3,500 to 4,500-watt heating elements, and they run on a 240-volt circuit. Therefore, you will need either a 20 to 25-amp (for 3,500-watts) or a 25 to 30-amp (for 4,500 watts) circuit breaker.

Regardless of the tank size, it’s essential to look at the label to get the correct power rating.

What Size Circuit Breaker For A 50-Gallon Water Heater?

The majority of 50-gallon water heaters will need a 25 to 30-amp circuit breaker. Most of these heaters have 4,500-watt heating elements.

But, since 50-gallon tanks are recommended for families of 3 to 4 people, aim for the 30-amp. It’s safe to assume your household uses a lot of water, so the larger breaker will avoid frequent tripping.

Why Do I Need A Circuit Breaker?

Your water heater uses electricity to heat the water, pushing electrons through the wires. If too much heat builds up in the wires, the wire covering can melt, starting a fire. Therefore, there needs to be a way to stop the electricity flow when there’s too much of it.

This is where a circuit breaker comes in, tripping to disconnect the water heater from the power source. It not only helps maintain the water heater’s performance and stability, but more importantly, it can save your home (and you) from a fire.

Why Is My Water Heater Tripping The Breaker?

If you have the correct size circuit breaker for your water heater, but it’s frequently tripping, it could be several things. But, no matter the cause, avoid flipping the breaker repeatedly; you could overheat the wires or damage the circuit breaker. 

This could lead to a fire or your circuit breaker not tripping in the future, leading to a damaged water heater. It also does you no good to replace the breaker with a higher-rated one. 

Doing this without replacing the circuit and wiring will lead to overheated wires and fires. Therefore, if your breaker keeps tripping, consult with a plumbing and electrical company.

Here are the primary reasons your water heater keeps tripping the breaker.

1. Faulty Wiring

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It’s possible that some of the wiring is loose, causing the breaker to trip. Or, in some cases, there could be damage to the wires. There’s also the possibility that the installer did not connect the wires appropriately during the installation process.

It’s best to have an electrician check all the connections and ensure everything is connected correctly.

2. Bad Thermostat

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As previously mentioned, water heaters running on 240-volts typically have two heating elements, one on top and one on the bottom. These elements are meant to run one at a time.

However, when the water heater thermostat goes bad, both heating elements start to run at once. This becomes more than the circuit breaker can handle, overloading it and tripping the breaker.

3. Heating Element Burns Out

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Usually, if one of your water heater’s heating elements burns out, your only clue might be cooler water. But, sometimes, the element’s casing splits, exposing the electrical to the water, resulting in a short circuit and tripping the breaker.

Do You Need A New Water Heater?

While a consistently tripping breaker doesn’t necessarily mean you need a new water heater, several other signs can point to replacement.

  • If your water is discolored, looks rusty, has a foul odor, or tastes off, you probably need a new water heater. These are all signs of a bad anode, and your water heater is starting to corrode.
  • You might need a new water heater if you no longer get hot water. First, check your pilot light, thermostat, and circuit breaker. But, otherwise, it’s likely a failed heating element.
  • If your water heater starts making loud cracking noises or pops, this indicates a failed heating element.
  • A leaking water heater is a major red flag. You need to shut it down, let it cool, and drain it to avoid further damage to your floors, etc. 
  • If you’re noticing some issues and your water heater’s at or beyond 10-years-old, it’s probably in your best interest to replace it. The average lifespan of a water heater is 10 years.

Frequently Asked Questions

Can I replace my water heater without a permit?

No, most cities require a permit for a water heater, whether a new install, replacement, or upgrade. It also is necessary whether you’re doing the install or using a professional, and often, you’ll have to get a pro to install it.

Permits ensure the installation meets specific safety guidelines and the installation is correct. An inspector will check all of the plumbing and electrical connections to ensure everything is to code.

Depending on what’s needed for the install, expect to pay anywhere from $50 to $500 for a permit. You can get the permit yourself, or often the professional installer will factor it into their costs.

How much does a new water heater cost?

There are numerous factors that influence the cost of a water heater. For example, the size of the tank, type of heater, power rating, and more all play into the final price tag.

On average, for a 50-gallon water heater, you’ll pay about $800-$900. But, overall, water heaters can range from $300 to $2,000 or more.

Then, you need to factor in the installation costs, which are usually about $45 to $150 an hour. An average installation will take about two to three hours.

With this in mind, a tank water heater can cost about $800 to $1,500 for the appliance and installation. Tankless heaters would be between roughly $1,000 and $3,000.

How do you determine the best size wire for a water heater?

In addition to choosing the correct circuit breaker, using the right wire for your water heater is also important. A 10/2 non-metallic cable is the recommendation for a 4,500-watt heater on a 240-volt circuit.

Keep in mind, the larger the number, the smaller the wire. In other words, a 10-gauge wire is thicker than a 12-gauge wire. So, it’s important to match the wire size to the amperage. For a 25 to 30-amp breaker, you need a 10-gauge, 20-amp can use a 12-gauge, and a larger, like a 40-amp, would require an 8-gauge.