What Size Breaker for Microwave? (15 amp vs 20)

Breakers are needed to manage the electricity supply between various appliances effectively. 

Microwaves generally require a 15 amp or 20 amp breaker size. The current standard for most microwave installations is a 20 amp breaker, which provides additional protection against electric surges. However, microwaves with larger energy requirements may need larger breaker sizes and a dedicated circuit. 

Stay safe by learning the proper breaker size for your microwave.

Selecting a Circuit Breaker for your Microwave

Two circuit breaker types are used for microwaves: the 15 amp and 20 amp breakers.

The power requirements of the microwave determine the appropriate breaker size to use. However, most electrical systems use a 20 amp breaker for all microwave types. That’s because a larger breaker won’t negatively impact the circuit and the microwave itself. On the other hand, using a smaller breaker will cause certain problems.  

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It’s generally preferred to use a 20 amp breaker for your microwave. 

The slightly larger 20 amp circuit breaker performs the same functions as the 15 amp one. The benefit of using the 20 amp breaker is its additional protection against electric surges. The breaker can handle the sudden burst of power without tripping or damaging the microwave. It also allows the microwave to run simultaneously with other devices in the room.  

Only go above a 20 amp breaker if the microwave requires it. 

Although you can use larger sizes, the difference between the breaker size and power requirements should be small. Using an excessively large size will prevent the breaker from tripping when needed. 

How Voltage and Amps Affect the Breaker Size

Your microwave’s voltage and amps requirement is needed to determine the appropriate breaker size. 

The microwave’s instruction manual states all the needed information on the voltage and amp. Some countries even require manufacturers to stick an energy label on the devices. This label contains all the key information on the device’s energy requirements. 

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Voltage is the pressure that pushes the electric current to flow from the outlet to the circuit. 

Microwaves are split into two voltage requirements: 120 and 240 volts circuits. The type of microwave determines the voltage requirement  – with smaller models typically using a 120 volts circuit. 

Amperage (amps) is the current flowing through the device’s circuit. 

According to the US National Electrical Code, microwaves usually have an amp requirement of 15 to 20 – with the lowest being at 10 amp. As stated before, 20 amp breakers are more commonly used due to their additional safety benefits. 

Energy Requirements of Different Microwave Types

Don’t just connect a 20 amp circuit breaker to the microwave and call it a day.

It is important to consider the size and type of microwave when selecting a breaker size. Using the correct breaker size will prolong the microwave’s lifespan and keep the household safe. Furthermore, larger microwave sizes may require a dedicated circuit to operate. [1]

A dedicated circuit can be compared to a permanent outlet to plug a certain device. It is used for devices that need high voltage power supply, such as refrigerators and powerful microwaves. Moreover, microwaves that need a dedicated circuit require larger breaker sizes. 

The size of the microwave is determined by its voltage requirement. 

500 to 800 Volts

These types of microwaves are small enough to be placed on countertops. 

These can be run using a 15 amp breaker or higher. In addition, you can plug it into any convenient nearby outlet. The low energy requirement enables it to be used alongside other kitchen appliances. You can freely add a ceiling fan to the outlet without worrying whether or not it will trip. 

800 to 1,200 Volts 

This type of microwave is mid-tier regarding size and energy requirements.  

These microwaves can function on a 15 amp breaker but are usually run on a 20 amp one. They don’t generally need a dedicated circuit to function. However, there’s nothing wrong with connecting it to a dedicated circuit. 

1,200 Volts and Above

These types of microwaves are powerful devices that have heavy energy requirements. 

These microwaves must be connected to a dedicated circuit. The circuit breaker size varies depending on the exact voltage requirement, but at least a 20 amp breaker is needed.

Hybrids such as microwave ovens are classified under this type. 

This is why certain companies offer installation services for appliances, microwave ovens, and the like. Adding electrical circuits to the kitchen is necessary if there are no available dedicated circuits. They should not share an outlet with another appliance. These microwaves are typically permanently fixed to a certain location. It could be above the stove or under a cabinet.

Effects of Installing the Wrong Breaker Size

Installing a smaller breaker size is less forgiving than installing a larger one. 

The microwave will continue to draw too much current for the small breaker to handle. This will result in frequent breaker trips. It’s also possible for the amp circuits to overheat and overload. Microwaves that use a high-voltage power supply are at further risk of causing electrical fires. 

The main risk of using breaker sizes that are too large is their trip threshold.

The breaker trip will not activate if the current flowing through is still within its acceptable limits. Meanwhile, the microwave connected to the breaker may have a different current limit. The microwave may already be experiencing circuit overload. To prevent this, the general recommendation is to minimize the difference between the microwave amp rating and circuit size. 

The US National Electrical Code requires household owners to use the appropriate breaker size for their appliances. This ensures not only the safety of the homeowner but the people around them as well. 

Take a look at some of our related articles below.


[1] Codes and Standards – National Fire Protection Association – www.nfpa.org/Codes-and-Standards 

Video References

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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