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What Size Breaker Does A Water Heater Need?

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Water heaters come in a variety of sizes. How do you choose the right one for your home?

A water heater is a large appliance that heats water for domestic purposes.

They are usually installed in basements or garages, where they are exposed to extreme temperatures.

The correct size of a water heater depends on several factors such as the number of occupants, the amount of hot water consumed, and the type of heating system.

There are two main types of water heaters: storage and instantaneous.

Storage water heaters store hot water until needed. Instantaneous water heaters produce hot water instantly. Both types require a specific capacity.

A water heater’s capacity refers to how much hot water it can supply at any given time. It also determines how long it will take to get hot water once the tank has been filled.

How Big Should My Water Heater Be?

What Size Breaker Does A Water Heater Need?

The U.S. Department of Energy (DOE) recommends that all households have a minimum capacity of 10 gallons per minute (GPM).

This means that if you use more than 10 GPM, you may want to add another unit.

If you only use 5 GPM, then you might not need a second unit.

Your local building codes may specify different requirements. For example, some cities require a minimum of 15 GPM.

In addition, many municipalities limit the maximum flow rate allowed by law.

The total volume of hot water produced by a water heater is called its “capacity.” The capacity of a water heater is measured in gallons per minute (GPM).

You must know the capacity of your current water heater before replacing it with a new model.

To determine this figure, multiply the number of people living in your house by the average daily usage.

For example, a family of four uses about 20 gallons of hot water each day. Their old water heater had a capacity of 50 GPM.

That means that their old water heater could provide enough hot water for four showers every day.

If you replace the old water heater with a new model, you can expect to save $100 on your monthly energy bills.

What Does A Water Heater Do?

Water heaters come in different sizes, and each size requires a specific breaker size.

Be sure to check the amperage of your heater before buying it. A hot water heater needs a high wattage breaker because it draws a lot of energy.

Wattage is measured by how much current (amperage) flows through a circuit. The higher the amperage, the greater the wattage.

You should also check the wire size, since it determines how many wires are needed. The wire size must be equal to the breaker size.

Electric Water Heaters require permits before being installed.

Inspections of installations must be completed by inspectors to ensure safety standards are met.

Standards vary depending on location but may include inspections of electrical connections, plumbing, gas piping, etc.

Electric style water heaters actually need a 240-volt circuit, which solely serves the water heater itself.

The circuit wiring usually includes a 30 amp double pole breaker and 10-2 NM/MC cable.

At the water tank, the black circuit wire attaches to the black wire lead, and the white circuit line attaches to the red or white lead.

The white circuit line should be wrapped with black tape near the connection at each end of the circuit (at the water heater and at the breakers).

This indicates that this is a hot wire, not a neutral. A 240V circuit carries live current in the two wires, unlike a 120V circuit.

The circuit ground wire attaches to the green ground screw of the water heater or to its ground lead.

Sizing Water Heater Breakers

Water heaters should be sized according to the amount of electricity needed by the house.

A 40-gallon water heater uses about 4500 watts (see also ‘4500 Vs 5500 Watt Water Heater‘) of power or about 18.75 amps. So if your house needs more than 18.75 amps, you’ll want to buy a bigger water heater.

Water heaters need 25 amps or more to work properly. We recommend using 30 amps for safety reasons.

An 80-gallon heater requires about 28 amps. This means you should use a 30 amp breaker.

How Do You Calculate The Breaker Sizing?

What Size Breaker Does A Water Heater Need?

You should always be aware of how many amps your appliance requires before buying it.

This information is usually available on the product label or packaging. 

You may be thinking, a water heater with a capacity of 25 gallons needs a breaker size with a value of 25 amps.

However, this is where overloading starts to happen. A water heater is supposed to operate at 125% of its maximum continuous load.

This means that if the water heater is operating at 100%, then you should use a breaker size of 125%.

In order to do this, we need to multiply the current draw by 1.25. So, 125% x 25 amps equal 31.25 amps.

We can now get the closest amperage size, which is 35 amps for a 35-amp circuit breaker.

For a 35-ampere circuit breaker, the Square D by SCHNEIDER ELECTRIC HOM235CP is recommended.

Water heaters should be wired according to the National Electrical Code (NEC).

You can use this table to determine the proper wire size based on the amperage of your water heater.

A water heater is a continuous (24/7) load device. To calculate the proper breaker size, divide the total power by the number of volts.

In this case, 4500 divided by 240 equals 18.75. Then multiply this figure by 125% to get 23.4 amps.

For continuous loads, use 25 amp or 30 amp breakers.

In order to properly size a circuit breaker for a continuous load, you must first determine what type of load you have (i.e., continuous vs. non-continuous).

Then, you need to calculate how much power your load requires. For example, if you’re running a clothes dryer, you may be looking at a continuous load.

However, if you’re running an electric stove, you might be dealing with a non-continuous load.

What Circuit Breaker Size Should Be For A Gas Tankless Water Heater?

A water heater needs to match its amperage to the wire size.

For example, a 15-amp heater requires a 14-gauge wire, while a 30-amp heater requires a 16-gauge wire (10-2).

Consider breaker size as well. Heaters up to 50-amps need 6-gauge wires.

Gas tankless water heating uses less energy than electric tank water heating. Usually, it’s about 12 amps and less than 120 volts.

Gas tankless water heaters need a minimum amount of electricity to power an electronic ignition system.

A gas tankless water heater only needs a single-pole breaker for this purpose.

Should You Get A Gas Water Heater Or An Electric Water Heater?

What Size Breaker Does A Water Heater Need?

Electric water heaters are more efficient than gas ones.

They require less maintenance but are more expensive than gas water heaters in the long term.

You need to consider how much money you want to spend upfront and how much you want to save later.

Instantaneous Vs. Storage Water Heaters

An instantaneous water heater produces hot water immediately when needed.

Instantaneous water heater models include gas-fired, electric, solar, and propane tanks.

Installed directly into the wall, these units are easy to install and operate.

Storage water heaters keep hot water ready for immediate use.

These appliances consist of an insulated tank containing a thermostatically controlled element.

When hot water is required, the element turns on, providing instant hot water.

Installing A Water Heater

Water heaters are heavy and bulky items that require professional installation.

Before you buy a new water heater, ask your plumber for help installing it.

He or she will explain what kind of connections you need to make and how to properly hook up the elements.

Water heaters come in three basic sizes: 30-, 40-, and 60-gallon models.

Most homes require a 30-gallon water heater. However, larger families may require a 40- or 60-gallon model.

Most residential water heaters are installed in the basement. Some models are designed to sit on top of the floor.

Others are mounted on concrete slabs. If you plan to move your water heater, check with your plumber first.

He or she may recommend moving it to a less accessible location.

If you live in an area where freezing temperatures occur during the winter months, consider purchasing a water heater that includes a safety shutoff valve.

This feature automatically shuts off the supply of fuel to the burner if the temperature drops below a certain point.

It also prevents the possibility of carbon monoxide poisoning from occurring.

A water heater is one of those things that most homeowners don’t really think much about until they need to change out their appliances.

But there’s no reason why you should be caught off guard like this. Here are some things to look at before making any big purchases.

Things To Consider Before Buying A Circuit Breaker

When choosing the right water heater breaker size, you should consider the amp difference between the heater and the breaker.

Too big a breaker could cause an electrical hazard. Too small a breaker would mean continuous tripping.

Don’t let the breaker share a circuit with other things. And please upgrade the breaker if needed.

A breaker with a higher amperage rating than needed means that there is a risk of overheating.

The breaker may ignore an immediate overheat condition because it thinks it isn’t dangerous enough to shut off the power. This could lead to a fire.

Final Thoughts

The best way to determine which size water heater to purchase is by consulting with a qualified heating contractor.

They can tell you which type of unit works best for your home. In addition, they’ll be able to give you tips on how to maintain it.

We hope that this article has given you an insight into what water breakers are and what size breaker a water heater actually needs to function in your home!

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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