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The accidental invention of the microwave

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Tara Dunker

Tara Dunker

As a mom of two tiny human wrecking balls (whom I love dearly), I take for granted how often my microwave saves me from drinking unintentionally cold coffee.

Those first few sips of piping hot caffeine are precious because, without a doubt, I’ll be interrupted a hundred times before seeing the bottom of my mug.

Thanks to a guy named Percy LeBaron Spencer who never finished elementary school but taught himself engineering decades before I was born, I can push a few buttons, wait about a minute, and enjoy my coffee all over again. And again, and again, and again—parents of young ones know what I mean.

Why am I talking about my microwave? Because next Tuesday, Dec. 6 is National Microwave Day. I’m shocked you didn’t know that already. To celebrate, I figured we’d all learn its history together.

According to Live Science magazine, sometime around 1941 our friend Percy was testing radar system parts called magnetrons when he noticed the chocolate bar in his pocket had melted. Surprised by this, he shifted his focus from radar systems to food.

He pointed the microwave energy produced by magnetrons at popcorn kernels. Spoiler alert—they all popped. He placed an egg near a magnetron and watched it rattle and shake before exploding.

Once he realized microwave energy was capable of cooking food, he built a metal box and directed the energy into it. All that energy entered the box but couldn’t escape because microwaves don’t pass through metal.

After countless experiments, Percy determined that microwaves not only cook food, they cook food faster than the heat produced by conventional ovens. This was a game-changer, and in 1945 he filed an application to patent his discovery.

A couple years later the first commercial microwave oven was built. You’re likely picturing a device similar to the one sitting on your kitchen counter or hanging above your oven, but in 1947 this revolutionary invention stood five and a half feet tall, weighed 750 pounds, and cost $5,000. According to a quick Google search, that’s worth about $66,818 today.

The Radarange 1161 (what a name!) even had to be hooked up to a water line because the magnetron technology wasn’t advanced enough to be cooled by any other method.

As you can imagine, it took a few years for the general public to trust this new technology, but once the foodservice industry recognized its many uses the machines began appearing in restaurants across the country. Kitchen staff were using microwave ovens to roast coffee beans and peanuts, defrost and pre-cook meats, and even shuck oysters.

Fast forward to 1955, and the first microwave oven for home use was introduced. However, because it was the size of a conventional oven and cost $1,295 (worth about $14,400 today) you can probably guess few were sold. A decade later, the company that originally employed Percy when he made his discovery acquired Amana Refrigeration and began selling the Amana Radarange which could fit on a kitchen countertop and cost less than $500.

As the size and price tag continued to shrink, the in-home microwave oven grew even more popular in U.S households than the dishwasher. While only 4% of homes had microwave ovens in 1975, more than 90% have one today. Thanks, Percy.

If you have any further questions, please contact Tara Dunker at 402-223-1384,, or visit the Gage County Extension website at


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