4500 Watt Hot Water Heater Breaker Size

A homeowner’s most common mistake when purchasing an electric water heater is not checking the amperage. It is common for heater tanks to only be labeled with their voltage and power requirements, but never their ampacity. in this guide, we will discuss 4500 Watt Hot Water Heater Breaker Size.


Understanding Your Water Heater

The best way to find your tank specifications is to ask your retailer or the brand manufacturer. You must determine your heater’s size first before determining your breaker’s size. There are three factors you need to consider to ensure safety:


In a healthy circuit, your boiler’s voltage plays a fundamental role. Based on your tank size and wattage, you can plug a heater into a 220 or 240 Volts outlet.


List the wattage requirement of your heater. Your device’s wattage can be an advantage if it typically uses a lot of power for its tank size and other features. It will make finding an appropriate breaker easier.

Wire Size- 

Finally, ensure that the hot water heater breaker size is compatible with your cable type. Reusing faulty wires or incompatible sizes can pose more risk to your heater and breaker than good.

What’s the formula for a Breaker Size Solution?

Making a simple calculation will help you determine the amp size you’ll use. If you are already using a water heater that has a wattage and voltage, you can use the Ampere formula: l (amps) = w/v (volts).

My heater tank needs 120-volt power, and it is 3,000 watts. Divvying watts by volts

gives you amperage.

I = PV

120 volts / 3000 watts

The current in I is 25 amps

If a device has 25 amps, you may think a breaker size that matches that value is required. Therein lies the source of overload and overstripping.

There is a restriction put forth by the National Electric Code (NEC) that states you must not exceed 125% of the maximum continuous load. The essential step to get the right electric water heater breaker size is to calculate the safe amount.

Apply the continuous load rule to the example above: 125% x 25 amps = 31.25 amps. Therefore, the nearest amp size would be 35 amps. Schneider Electric’s Square D by Schneider Electric HOM235CP is a highly recommended product for 35-amp CBs.

If your 25A water heater is connected to a 20-amps breaker, expect that it will trip frequently. It will allow a power surge to pass through without tripping your breaker.

For a better understanding, watch this video from House Wiring T.V. : correct way to size your water heater wires and


How large is the breakers for 40 and 80-gallon water heaters?

Water heater tanks typically range from 40 to 80 gallons, depending on how much hot water is used every day by a family.

When finding out how many amps to use for water heaters of these tank sizes, you must know their wattage and voltage, then apply the solution earlier. Using the earlier solution, you can find out how many amps a water heater needs based on its wattage and voltage.

With 240 volts, a 40-gallon heater operates on an average of 4500 Watts. Assuming I = P/V, 4500W/240V equals 18.75 amps. Taking into account the continuous load (125% x 18.75A), we’ll get 23.4 amps.

The nearest equivalent amperage value for a 40-gallon water heater is a 25-amp breaker. For a safer breaker size, I recommend to use 30-amps.

Using 240 volts and 5500 watts

, an 80-gallon heater consumes 12.5 amps per continuous load, which equals 28.64 amps. Therefore, a 30-amp dedicated circuit breaker is sufficient.

An 80G tank will not be protected by a 40A breaker, despite the fact that a 30A breaker may sound inadequate. A surge in power will not trip breaker amperage much higher than necessary will not trip.

When wiring a water heater, what wire size is best?

If the wiring is incompatible, a water heater can’t be connected to its breaker. Your heater’s amperage must match its wire size. Here are some suggestions:

  • A 20-amp circuit requires a 12-gauge wire
  • Wire of 10-gauge can handle 25 amps
  • An 8-gauge wire is suitable for 30/40 amps
  • Wiring for other large heaters up to 50 amps requires 6-gauge

Consider your water heater’s breaker size, too. For large boiler tanks, 30 A circuit breakers require a 10-2 nonmetallic or MC cable. A start load of 40-amps and a constant load of 35-amps can be handled by this type of wire.

4500 Watt Hot Water Heater Breaker Size

Circuit breakers: Preventive measures before buying

You must consider the amp difference between the circuit breaker and the heater when choosing the right water heater circuit breaker size. The correct size must be selected. The wrong size or number of breakers can create an electrical hazard.

Your breaker will trip continuously if it is too small for the heater’s amperage requirement. Moreover, too much on/off of the heater can result in internal damage. It is best not to share a circuit with your water heater with other appliances, and upgrade the circuit breaker if necessary.

There is no guarantee that a breaker with a higher amperage than intended is safe for a heater. If the tank suddenly has a short circuit or overload, your breaker will disregard the event — no protection at all.

Frequently Asked Questions (FAQs)

What Size Breaker Do I Need For A 4500 Watt Water Heater?

30 amps

The right circuit breaker for this appliance with 4500 watts at 240 volts is either 25 amps or 30 amps. If the water heater isn’t rated as “continuous load”, then it would have been fine to use 100% of the circuit breaker’s rating

What is the amperage draw of a 4500 watt water heater?

18.75 amps

4500 watts is the average power output of an electric 50 gallon water heater. On 240 volt circuits, 4500 watts equal 18.75 amps.

Can I Use A 40 Amp Breaker For My Water Heater?

Be sure to consider the size of your water heater’s breaker. In large boiler tanks, 30 amp circuit breakers are usually used with 10-2 non-metallic or MC cables. It is suitable for load starts of 40 amps and constant loads of 35 amps

What Size Circuit Breaker Do I Need For A Hot Water Heater?


For electric water heaters to function, a 240-volt circuit is required. The circuit wiring includes a 30-amp double-pole breaker and 10-2 non-metallic cable.

Final Verdict: 4500 Watt Hot Water Heater Breaker Size

Knowing what size breaker to use for a water heater isn’t difficult as long as you gather the right information. You can determine the proper breaker size by understanding the three wire heater elements – voltage, wattage, and wire size.

This can also be done with a simple calculation, but be sure the breaker size is close to the answer (the actual amp size of the heater).

As most electric water heaters use 30-amp breakers, an electrical circuit breaker with a double pole type QP breaker like the Q230 will be suitable.

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