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Percy Spencer: The Man Who Accidentally Invented the Microwave Oven

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Percy Spencer and first commercial microwave oven

Percy Spencer and first commercial microwave oven

Who Invented the Microwave?

Percy Spencer was a self-taught engineer who was hired by the Raytheon company in the 1920s. His hard work and success led him to become one of the company's most well-known and valued workers. Spencer had a reputation as a gifted problem solver and helped develop many important items for the military. One such device was detonators that enabled soldiers to trigger artillery shells, so they could explode before hitting their mark in mid-air. When he was testing a device called a magnetron, he noticed the microwaves from the device melted the chocolate bar he had in his pocket. Spencer was curious about why this happened. He continued testing other foods such as an egg, that exploded and covered his face. The next day he brought corn kernels for testing. The magnetron microwaves popped all of them. Everyone in the office where he worked wanted to use their food on Spencer's invention.

And so the microwave was created.

Early Life

In 1894, Percy Spencer was born in Howland, Maine. At the age of 12, he dropped out of grammar school. Spencer then went to work in a weaving mill as a spindle boy. As a young man, he worked hard at teaching himself about electricity. Spencer became very skilled and was asked by a local paper mill to set up their new electrical system. He was 18 when he joined the U.S. Navy in 1912. Spencer worked as a naval radio operator. During this time, he was busy using his free time to study many different scientific subjects. They included trigonometry, calculus, physics, chemistry as well as metallurgy, and more. While standing watch late at night, Spencer would also read textbooks that he had obtained.



American Appliance Company

Spencer joined the American Appliance Company in Cambridge, MA soon after World War I ended. This company soon became known as the Raytheon Company. The British signed a contract during World War II with Raytheon for the company to mass-produce one of their latest inventions: combat radar equipment. Britain was in a difficult situation in the war and in need of a way to detect German submarines as well as planes. The primary component in their combat radar system was the magnetron. Spencer created a way for the magnetron to be produced on a large scale. At its peak, over 2,500 were being manufactured in a day. A Commodore from the U.S. Navy stated the radar equipment produced by Raytheon had a significant impact on all sea engagements during World War II. Spender was awarded the Distinguished Public Service Award from the U.S. Navy. This is the highest civilian honor that can be given to a civilian by the Navy.

Microwave Discovery

The discovery happened when Spencer was busy building magnetons. He was standing at the front of a radar set testing it. This is when he realized the snack in his pocket melted. Others had noticed such a phenomenon occurring, but Spencer was the first person to begin investigating it. Spencer tried different foods including popcorn kernels. He then placed the high-density electromagnetic field inside of a metal box. This was the world's first microwave oven. Spencer discovered the magnetron was able to emit microwaves into the metal box. Doing this blocked the escape of the microwaves. This made it possible to have safe and controlled experimentation. During the following days, he put different food items in the metal box. He would observe the effects of the microwaves on the food and monitor their temperatures.

Microwave drawing

Microwave drawing


On October 8, 1945, Raytheon filed a patent for a microwave cooking oven. The name it was given was the Radarange. The first commercial microwave oven was built in 1947. It weighed approximately 750 pounds and was 6 feet tall. The cost of a Radarange at this time was $5,000. The first affordable microwave oven was released in 1967. It cost $495. Its size was small enough to be put on a countertop.

1967 microwave oven

1967 microwave oven


Spencer was eventually made a Senior Member of Raytheon's Board of Directors. He was also made a Senior Vice President. During his career, Spencer obtained over 300 patents. There is a building in Woburn, Massachusetts at Raytheon's Missile Defense Center that is named in his honor. The University of Massachusetts gave Spencer an honorary Doctor of Science, he was also given a Fellowship in the Academy of Arts and Sciences. His achievements were impressive considering he had no formal education.

No Royalties

For his work associated with inventing the microwave oven, Spencer was not given any royalties. Raytheon gave him a one-time gratuity of $2.00. This is what the company paid all those employees at the time who created things the company could obtain a patent for inventing.


Percy Spencer died on September 8, 1970. He was 76 years old. He was buried after a service at St. John's Episcopal Church.

Microwaves being manufactured

Microwaves being manufactured

The majority of households in North America have a microwave oven in their home. Most homes around the world as well as businesses have one. It is a popular appliance for reheating previously cooked foods. A microwave is also often used to cook a variety of foods. The world of food preparation was changed forever by Percy Spencer’s invention of the microwave oven.


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Eric Dierker from Spring Valley, CA. U.S.A. on September 24, 2020:

Right on, what a cool dude. I always wondered about the radar range.

Readmikenow (author) on September 23, 2020:

Cheryl, thanks.

Readmikenow (author) on September 23, 2020:

Danny, thanks.

Cheryl E Preston from Roanoke on September 23, 2020:

I had no idea. Thank you for this story from history, it is truly amazing.

Danny from India on September 23, 2020:

Nice article

Readmikenow (author) on September 23, 2020:

Pamela, thanks. I agree.

Pamela Oglesby from Sunny Florida on September 23, 2020:

Percy Spencer was obviously a brilliant man, even without a formal education. This is a very interesting article, Mike.