Wire and Breaker Size for Microwaves: Complete Guide

Your kitchen, in general, requires more electricity to operate than any other room in your house. The high electricity load is because you have lots of high-powered appliances and equipment that you use simultaneously. An electric range, a dishwasher, a refrigerator, and a microwave all take a ton of electricity. Microwaves especially are deceptive in the amount of power they need. 

Microwaves require either a 15 amp breaker or a 20-amp breaker, depending on their wattage requirements. Microwaves that use 600 to 700 watts can get by with a 15-amp breaker, but microwaves that use over 700 watts should have a 20-amp breaker. Regardless of what size breaker you use, you should always power your microwave with a 12/2 gauge wire. 

Even though a 15-amp breaker is usually enough to power smaller microwaves, you should stay on the safe side and always install a 20-amp breaker. Installing a 20-amp breaker for a microwave has become the new norm in electrical work because there’s nothing wrong with installing a breaker that’s too big, but you’ll have big problems installing one too small. 

Standard Breaker and Wire Size for a Microwave Oven

Even though some microwaves only require a 15-amp breaker to power them, it’s common practice to install a dedicated 20-amp breaker. Installing a breaker that’s slightly larger than you need will ensure that a surge of power doesn’t trip the breaker or damage your microwave. It will also make it so that you can power your microwave simultaneously with other devices in your home and kitchen. 

Having the correct wire size running to your microwave is as essential as having the right breaker size. For both 15 and 20-amp circuits, you should have a 12/2 gauge NM wire running from the breaker to the outlet powering your microwave. Make sure that your outlet can handle a 20-amp circuit and has a spot to attach the ground wire. 

Different Types of Microwaves and Their Power Requirements

Saying that all microwaves need a dedicated 20-amp circuit and 12/2 NM wire might seem a little cut and dry. Can’t you just plug your microwave into whatever outlet is nearby? Sometimes you can, and sometimes you can’t. The size and type of your microwave will determine its breaker and wire requirements. 

500 to 800-Volt Microwaves 

Most modern kitchens have microwaves with dedicated circuits and a specific outlet. Dedicated circuits usually apply to larger microwaves installed in a specific and permanent location. However, you don’t need a dedicated circuit or breaker for smaller microwaves that use 500 to 800 volts of electricity. 

Microwaves of this size usually sit on countertops or kitchen tops, and you can plug them into wherever is convenient. As long as it’s plugged in in your kitchen, you can rest assured that the wire and breaker powering are large enough. 

800 to 1,200-Volts Microwaves 

800 to 1,200-volt microwaves are a little tougher to peg as far as wire and breaker size. If you want to be on the safe side, you should have a dedicated circuit running to the microwave with a 12/2 wire and a 20-amp breaker. However, you can usually get by with a 15-amp breaker if necessary. 

1,200+ Volt Microwaves 

For microwaves that are 1,200 volts or larger, you should have a 20-amp breaker with a dedicated circuit. These microwaves are usually mounted in permanent locations, above your stove, under a cabinet, or somewhere else in your kitchen. Some microwaves of this size are also hard-wired and bypass the need for an outlet. 

At any rate, microwaves that are 1,200 volts or larger need a dedicated 20-amp circuit and a 12/2 NM wire. 

Why do Microwaves Need Their Own Circuit? 

Technically, microwaves don’t always need their own circuit. If you have a smaller microwave that uses less than 600 watts, running a dedicated circuit is a waste of breaker box space. When your microwave needs its own circuit, you have one that uses upwards of 1,200 or 1,500 watts of electricity. 

You need a dedicated circuit because you won’t be able to power anything else on the same circuit as the microwave while it’s running. Your microwave will consume too much power and could cause your breaker to trip. 

I know firsthand the struggles of trying to operate a microwave on a circuit that’s too small to handle it. You’re constantly running back and forth from your kitchen to your basement to reset a tripped breaker, hoping that you don’t overload your electrical system and ruin something. 

Risks of Installing a Breaker That’s Too Small 

Thanks to advancements in the practices and components used in electrical work, the risks of a breaker or wire being too small aren’t as bad as they once were. In older houses with outdated electricity, you ran the risk of having your electrical wire overheating and starting a fire if your breaker or wire weren’t the right sizes. 

Nowadays, however, the biggest risk of installing a breaker or wire that’s too small to power your microwave has the breaker trip. A tripped breaker is an inconvenience, but it’s also a safeguard against the alternative, which is an overheated wire. 

Don’t Forget About the Wire

It’s equally important to have the correct size wire powering your microwave outlet. In modern kitchens, 12/2 NM wire has become the standard. It’s the perfect size in that it will never be too big or too small to power a microwave. A wire of this size will also ensure that it will not get overworked and run the risk of overheating. 

Related Questions 

Does a microwave need a 15 or 20-amp circuit? 

While some microwaves only require a 10 or 15 amp circuit, it’s always best to stay on the safe side and install a 20-amp circuit. 

Do microwaves need a 20-amp outlet? 

Modern outlets are capable of handling 15 or 20-amp circuits equally well. 

Final Thoughts 

Microwaves are handy kitchen appliances that use more power than you would expect based on their compact size. For that reason, you must have the right size breaker and wire powering it. If you’re unsure what the voltage and amp requirements are for your microwave, you should stay on the safe side and run it on a 20-amp circuit. 

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.
DISCLAIMER: The content published on HomeInspectionInsider.com is not professional advice. You should consult with a licensed professional and check local permit requirements before starting any project.
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