How many Amp Breakers are for a Water Heater? (+ What Size Breaker Needed?)

A person does face many problems in case of the electrical water heater getting tripped due to overload. So this article will guide you about the size breaker of a hot water heater you need to have.

How many amp breakers are for a water heater? 

On average most electric water heater can be worked with a 30 amps breaker. But actually, the size of the breaker of the Water Heater does vary and depends on the type and wattage, and voltage drawn by the electrical heater.

Water Heater
Water Heater


The formula for calculating the amp size of the water heater:

If a person doesn’t have any idea of amps then they can easily calculate it. As the wattage and voltage are mentioned on the label of the heater so you just need to apply this formula to calculate the ampere:

Amps = watts/volts. 

Water Heater
Water Heater

Let’s understand it with an example the heater tank is 3000 watts and needs 120-volt power than for getting the ampere. 

Amps (I) = 3000 watts / 120 volts then

I = 25 amps. 

But it is not necessary that for a water heater that draws 25 amperes you will use a 25 amps breaker this is why the circuit trip. According to the national electric code, the amp breaker size should be 125% of the maximum continuous load. For example, the breaker size will be 125% * 25 amps = 31.25 amps. Hence you can use an amp breaker size of 35 amps and the Square D by Schneider Electric HOM235CP S is the best 30 amp. The following video explains how to use the size breaker with the water heater.

How many amps should we use with a 40 and 80-gallon water heater? 

A standard water heater does need an ampere of 18.8 amps with 120 volts to function but a gas water heater needs an ampere of 12 amps or 115 volts. The amperage used by a water heater does depend on the fuel type and size of the tank. If a 40-gallon heater has a wattage of 4500 watts on average with 240 volts then using I = P / V, the ampere used is 18.75 amps and for amp breaker size 125% * 18.75 A = 23.4 amps. So the least amount of amp breaker is 25 but using a 30 amp breaker will be safer. And for an 80-gallon heater on average wattage will be 5500 watts and 240 volts then it needs a 30 amp dedicated circuit breaker. 

The following chart shows the different water heater sizes and different breaker sizes them:

Water Heater SizeBreaker Size
10 Gallon Water Heater20 Amp Or 30 Amp
20 Gallon Water Heater20 Amp Or 30 Amp
30 Gallon Water Heater30 Amp Breaker
40 Gallon Water Heater30 Amp Breaker
50 Gallon Water Heater30 Amp Breaker
60 Gallon Water Heater30 Amp Breaker
70 Gallon Water Heater30 Amp Breaker
80 Gallon Water Heater30 Amp Breaker
90 Gallon Water Heater30 Amp Breaker Or Bigger
100 Gallon Water Heater30 Amp Breaker Or Bigger
Water Heater
Water Heater

What wire size should be used for a water heater? 

Using a perfect-size of breaker with a water heater will not work properly unless the wiring is not compatible. So it would be best if you match the amperage of the heater with the wire size. The wire size according to the amperage of the water heater:

  • A water heater of 20 amps needs a 12 gauge wire. 
  • A water heater of 25 amps needs a 10 gauge wire. 
  • A water heater of 30/40 amps needs an 8 gauge wire. 
  • All the heater larger than 50 amps needs a 6 gauge wire

Things to be prevented before buying a circuit breaker:

  • Before buying a circuit breaker you should know the difference between the amp of the breaker and the heater and according to that should bring the right size of the circuit breaker.
  • As if it is not the right size there is an electrical hazard even if the breaker is too large or too little. If the breaker size is too small to use with water heater amperage it will trip continuously and due on and off of the heater it damages the heater internally. 
  • Prevent the use of a water heater sharing the circuit with other appliances. 
  • Use an upgraded breaker. 

What size breaker should be used with a 240-volt heater? 

The breaker size to be used with the heater should be 125% larger than the rated circuit. If a person is using a single 240-volt heater then a 20 amps breaker is good with it. A single 20 amp circuit can support 1500 watts of the heater and two heaters of 1000 watts. In the same way, a 40 amp circuit can support 3 heaters of 1500 watts and two 1000 watts of heaters. 

Water Heater
Water Heater


A person who wants to get a perfect size breaker for Water Heater by which they will not suffer from any electrical damage should know about the three wire heaters elements such as voltage, wattage, and wire size according to it they will get a proper size breaker and from the above reading you know have complete knowledge about them all. 


How many amps are used by a water heater? 

A typical-size of water heater uses 18.8 amps. 

Rick Costa

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