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What Size Inverter Do I Need to Run a Microwave? Our EASY Guide

The last thing you want to do is set up your off-grid system only to find that your inverter isn’t powerful enough to run your trusty microwave.

All microwaves are different, but the average 1,000-watt microwave will run using a 1,500 to a 2,000-watt inverter. To make sure you end up with the right inverter, let’s take a look at how to determine what size inverter you need to run a microwave.

Power Inverter For Microwave

Determining What Size Inverter You Need to Run a Microwave

At some point, many of us who enjoy off-grid living have asked, “What size inverter do I need to run a microwave?”

Fortunately, it’s incredibly easy to figure out what size sine wave inverter you need to run a microwave. Naturally, you’ll start by taking a look at the microwave itself.

Figure Out the Microwave’s Continuous Wattage Rating

The first thing you’ll need to figure out is how many watts the microwave uses while running, which is usually as easy as finding where it’s noted. This can be on:

  • The inside of the microwave door
  • The serial number tag on the back
  • The user manual
  • The manufacturer’s website

If you’re unable to find it after looking in all of these places, you can get a pretty good idea using the USDA recommended method: “Time-to-Boil Test.” It involves placing one cup of ice-cold water in the microwave and waiting for it to boil.

If water boils:

in less than 2 minutes = very high wattage oven (1000 watts or more).
in 2½ minutes = high wattage oven (800 watts or more).
in 3 minutes = average wattage oven (650 – 700 watts or more).
in 3 – 4 minutes = slow oven (300 to 500 watts).

Now you should have a pretty good idea of your microwave’s continuous wattage rating. However, there are other factors to keep in mind when answering the question “What size inverter do I need to run a microwave?”

Power Consumption Versus Cooking Power

It’s important to note that a microwave’s cooking wattage is lower than the wattage it consumes, so take that into account when choosing an inverter size.

Most microwaves use energy with about 80% efficiency (2). So if you’re unable to find your microwave’s power consumption noted anywhere, multiply the cooking wattage by .8 and add the total to the cooking wattage.

Say you have a microwave that cooks at 700w.
700w x .80 = 560w
560w + 700w = 1,260w
That means your actual power consumption is around 1,260w.

Interestingly, even though they require more power to run than they use to cook food, microwaves are still one of the more energy-efficient cooking methods, making them ideal for off-grid living. Scientific American states in a recent article:

Cooking or re-heating small portions of food in the microwave can save as much as 80 percent of the energy used to cook or warm them up in the oven.

That said, your microwave’s power consumption is what you need to worry about when choosing a sine wave inverter size, not the cooking power.

Conversion Formula

If you’re not able to determine your microwave’s wattage but know how many AMPS it uses, there’s an easy conversion formula that will help you figure it out.

Just multiply the AMPS by AC voltage, which is 120. The product is your wattage.

So if your microwave uses 12.5 AMPS, the formula would be:
12.5 AMPS x 120V = 1,500w

Factor In the Microwave’s Peak Wattage

Now that you know everything there is to know about determining your microwave’s continuous power usage, which is the power it consumes while running, it’s time to take a look at its peak wattage or the maximum amount of power it utilizes.

Peak wattage usually occurs during startup and lasts for less than a second, but your inverter needs to be able to handle this surge in power. The process should look something like this, if you need a visual:

Ultimately, when you’re looking for sine wave inverters, you’ll notice on the specs sheet that both continuous and peak capability are listed, so it should be easy to tell if it’s large enough.

Your microwave’s peak energy requirements should be listed on the owner’s manual or manufacturer’s website. If not, it’s a good idea to choose an inverter that can handle two to three times its continuous wattage just to be on the safe side.

FAQs

A 1500-watt power inverter should be able to run a 700-watt microwave with no problem. You can use a pure sine wave inverter or modified sine wave inverter, but the modified sine unit may cause your microwave to run less efficiently.

You can use a modified sine wave inverter or a pure sine wave inverter to run a microwave, as long as they have a large enough capacity, aka battery power. When you compare pure sine inverters vs modified sine inverters, modified sine models tend to shorten appliances’ lives, so that’s important to keep in mind.

For more tips to get the most out of your home’s appliances, check out our Homepage.

Your inverter is big enough to run your microwave if it can handle its startup surge, and continuous wattage draw while it’s cooking. If your modified sine wave inverter or pure sine wave inverter can handle both successfully, you’re all set for your next road trip!

To help all this sink in, you can check out this guide that shows how to size an inverter to run a TV for a similar example.

  1. How Do You Determine the Wattage of Your Microwave Oven? Retrieved from: https://ask.usda.gov/s/article/how-do-you-determine-the-wattage-of-your-microwave-oven
  2. Physics of the microwave oven. Retrieved from: http://clas.sa.ucsb.edu/docs/default-source/tutor-resources-files/physics_of_microwave_oven.pdf?sfvrsn=17582bfb_2
  3. Stove versus Microwave: Which Uses Less Energy to Make Tea? Retrieved from: https://www.scientificamerican.com/article/stove-versus-microwave-energy-use/
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