Editing Microwave oven (section)

== History ==

=== Early developments ===
{{multiple image
| align = right
| direction = horizontal
| header   =
| image1   = Cooking with radio waves - Chicago Worlds Fair 1933.jpg
| width1   = 200
| image2   = Cooking with radio waves - Short Wave Craft Nov 1933 cover.jpg
| width2   = 200
| footer    = Demonstration by Westinghouse of cooking sandwiches with a 60 MHz shortwave radio transmitter at the [[1933 Chicago World's Fair]]
}}

The exploitation of high-frequency [[radio wave]]s for heating substances was made possible by the development of [[vacuum tube]] [[radio transmitter]]s around 1920. By 1930 the application of [[short wave]]s to heat human tissue had developed into the medical therapy of [[diathermy]].  At the [[1933 Chicago World's Fair]], [[Westinghouse Electric Corporation|Westinghouse]] demonstrated the cooking of foods between two metal plates attached to a 10&nbsp;kW, 60&nbsp;MHz [[shortwave]] [[transmitter]].<ref>{{cite journal | title = Cooking with Short Waves | journal = Short Wave Craft | volume = 4| issue = 7 | page = 394 | date = November 1933 | url = http://www.americanradiohistory.com/Archive-Short-Wave-Television/30s/SW-TV-1933-11.pdf | access-date = March 23, 2015}}</ref>  The Westinghouse team, led by I. F. Mouromtseff, found that foods like steaks and potatoes could be cooked in minutes.<ref>{{Cite journal |last1=Lovelock |first1=J. E. |last2=Smith |first2=Audrey U. |name-list-style=vanc |year=1956 |title=Studies on Golden Hamsters during Cooling to and Rewarming from Body Temperatures below 0 degrees C. III. Biophysical Aspects and General Discussion |journal=Proceedings of the Royal Society of London. Series B, Biological Sciences |volume=145 |issue=920 |pages=427–442 |bibcode=1956RSPSB.145..427L |doi=10.1098/rspb.1956.0054 |issn=0080-4649 |jstor=83008 |pmid=13359396 |s2cid=6474737}}</ref>

The 1937 United States patent application by Bell Laboratories states:<ref>{{US patent|2147689}} Chaffee, Joseph G., ''Method and apparatus for heating dielectric materials'', filed August 11, 1937; granted February 21, 1939</ref>
{{Blockquote|This invention relates to heating systems for dielectric materials and the object of the invention is to heat such materials uniformly and substantially simultaneously throughout their mass. ... It has been proposed therefore to heat such materials simultaneously throughout their mass by means of the dielectric loss produced in them when they are subjected to a high voltage, high frequency field.}}

However, lower-frequency [[dielectric heating]], as described in the aforementioned patent, is (like [[induction heating]]) an [[electromagnetic]] heating effect, the result of the so-called [[near and far field|near-field]] effects that exist in an electromagnetic cavity that is small compared with the [[wavelength]] of the electromagnetic field. This patent proposed radio frequency heating, at 10 to 20 [[megahertz]] (wavelength 30 to 15 meters, respectively).<ref name=  "patent">{{citation | url = http://pdfpiw.uspto.gov/.piw?PageNum=0&docid=02147689&IDKey=49D95666A76C&HomeUrl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO2%2526Sect2%3DHITOFF%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-adv.htm%2526r%3D1%2526p%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D2147689.PN.%2526OS%3Dpn%2F2147689%2526RS%3DPN%2F2147689 | publisher = United States Patent and Trademark Office | title = 2,147,689: Method and Apparatus for Heating Dielectric Materials | first = Joseph G. | last = Chaffee | date = February 21, 1939 | access-date = February 5, 2015 | archive-date = March 19, 2022 | archive-url = https://web.archive.org/web/20220319201814/https://pdfpiw.uspto.gov/.piw?PageNum=0&docid=02147689&IDKey=49D95666A76C&HomeUrl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO2%2526Sect2%3DHITOFF%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-adv.htm%2526r%3D1%2526p%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D2147689.PN.%2526OS%3Dpn%2F2147689%2526RS%3DPN%2F2147689 | url-status = dead }}</ref> Heating from microwaves that have a wavelength that is small relative to the cavity (as in a modern microwave oven) is due to "far-field" effects that are due to classical [[electromagnetic radiation]] that describes freely propagating light and microwaves suitably far from their source. Nevertheless, the primary heating effect of all types of electromagnetic fields at both radio and microwave frequencies occurs via the dielectric heating effect, as polarized molecules are affected by a rapidly alternating electric field.

=== Cavity magnetron ===
{{Main|Cavity magnetron}}
[[File:Original cavity magnetron, 1940 (9663811280).jpg|thumb|The [[cavity magnetron]] developed by [[John Randall (physicist)|John Randall]] and [[Harry Boot]] in 1940 at the [[University of Birmingham]], England]]

The invention of the [[cavity magnetron]] made possible the production of [[electromagnetic wave]]s of a small enough [[wavelength]] ([[microwave]]s). The cavity magnetron was a crucial component in the development of short wavelength [[radar]] during [[World War II]].<ref>{{cite web | url = http://histru.bournemouth.ac.uk/Oral_History/Talking_About_Technology/radar_research/the_magnetron.html | title = The Magnetron | work = Radar Recollections - A Bournemouth University/CHiDE/HLF project | publisher = Defence Electronics History Society (formerly CHiDE)}}</ref> In 1937&ndash;1940, a multi-cavity magnetron was built by British physicist [[John Randall (physicist)|Sir John Turton Randall, FRSE]] and coworkers, for the British and American military radar installations in World War II.<ref name="Magnetron"/> A higher-powered microwave generator that worked at shorter [[wavelength]]s was needed, and in 1940, at the [[University of Birmingham]] in England, Randall and [[Harry Boot]] produced a working prototype.<ref>{{cite journal|last=Willshaw|first=W. E.|author2=L. Rushforth|author3=A. G. Stainsby|author4=R. Latham|author5=A. W. Balls|author6=A. H. King|title=The High-power Pulsed Magnetron: Development and Design for Radar Applications|journal=Journal of the Institution of Electrical Engineers - Part IIIA: Radiolocation|year=1946|volume=93|issue=5|doi=10.1049/ji-3a-1.1946.0188|url=https://ieeexplore.ieee.org/document/5299321|access-date=June 22, 2012|pages=985–1005|archive-url=https://web.archive.org/web/20180505184050/https://ieeexplore.ieee.org/document/5299321/|archive-date=May 5, 2018 |issn=2050-5485}}</ref> They invented a [[vacuum tube|valve]] that could produce pulses of microwave radio energy at a wavelength of 10&nbsp;cm, an unprecedented discovery.<ref name="Magnetron">{{cite news|title=Briefcase 'that changed the world'|url=http://news.bbc.co.uk/1/hi/sci/tech/6331897.stm|publisher=BBC|date=October 20, 2017}}</ref>

[[Sir Henry Tizard]] traveled to the US in late September 1940 to offer Britain's most valuable technical secrets including the cavity magnetron in exchange for US financial and industrial support (see [[Tizard Mission]]).<ref name="Magnetron"/> An early 6&nbsp;kW version, built in England by the [[General Electric Company]] Research Laboratories, [[Wembley]], London, was given to the [[U.S. government]] in September 1940. The cavity magnetron was later described by American historian James Phinney Baxter III as "[t]he most valuable cargo ever brought to our shores".<ref>{{cite book|first=James Phinney III|last= Baxter|title=Scientists Against Time|location= Boston|publisher=Little, Brown, and Co.|year= 1946|page= 142}}</ref> Contracts were awarded to [[Raytheon]] and other companies for the mass production of the cavity magnetron.

=== Discovery ===
[[File:Wall of microwaves.JPG|thumb|Microwave ovens, several from the 1980s]]
In 1945, the heating effect of a high-power microwave beam was independently and accidentally discovered by [[Percy Spencer]], an American self-taught engineer from [[Howland, Maine]]. Employed by [[Raytheon]] at the time, he noticed that microwaves from an active radar set he was working on started to melt a [[candy bar]] he had in his pocket. The first food deliberately cooked by Spencer was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.<ref>{{cite magazine|magazine=Reader's Digest|date=August 1958|url=http://members.aol.com/spencerlab/history/readdig.htm|title=Percy Spencer and His Itch to Know|author=Don Murray|access-date=January 14, 2025|archive-date=March 6, 2005|archive-url=https://web.archive.org/web/20050306112532/http://members.aol.com/spencerlab/history/readdig.htm|url-status=bot: unknown}}</ref><ref>{{cite web| url=http://www.gallawa.com/microtech/history.html | url-status=dead | archive-url=https://web.archive.org/web/20110709081022/http://www.gallawa.com/microtech/history.html | archive-date=July 9, 2011 |title=The History of the Microwave Oven |first=John Carlton|last= Gallawa |year=1998}}</ref><ref>{{YouTube|4h1ESUz2H3E|Radar — Father of the Microwave Oven}}</ref>

To verify his finding, Spencer created a high-density electromagnetic field by feeding microwave power from a magnetron into a metal box from which it had no way to escape. When food was placed in the box with the microwave energy, the temperature of the food rose rapidly. On October 8, 1945, Raytheon filed a United States patent application for Spencer's microwave cooking process, and an oven that heated food using microwave energy from a magnetron was soon placed in a Boston restaurant for testing.<ref>{{US patent reference |number=2495429 |y=1950 |m=January |d=24 |inventor=Spencer, Percy L. |title=Method of treating foodstuffs}}</ref>

=== Commercial availability ===
[[File:NS Savannah microwave oven MD8.jpg|thumb|left|upright|Raytheon RadaRange aboard the [[NS Savannah|NS ''Savannah'']] nuclear-powered cargo ship, installed circa 1961]]
In 1947, Raytheon built the "Radarange", the first commercially available microwave oven.<ref>{{cite web| url=http://www.raytheon.com/ourcompany/history/leadership/ |archive-url=https://web.archive.org/web/20130322044917/http://www.raytheon.com/ourcompany/history/leadership/ |archive-date=March 22, 2013 |title=Technology Leadership |publisher=Raytheon}}</ref> It was almost {{convert|1.8|m|ftin}} tall, weighed {{convert|340|kg|lb}} and cost about US$5,000 (${{formatnum:{{Inflation|US|5000|1947|r=-3}}}} in {{Inflation-year|US}} dollars) each. It consumed 3 kilowatts, about three times as much as today's microwave ovens, and was water-cooled. The name was the winning entry in an employee contest.<ref>{{cite book|last= Gallawa|first= J Carlton|chapter= A Brief History of the Microwave Oven|title= The complete microwave oven service handbook: operation, maintenance, troubleshooting, and repair|chapter-url= http://www.smecc.org/microwave_oven.htm|location= Englewood Cliffs, N.J.|publisher= Prentice Hall|date= 1989|access-date= October 11, 2017|isbn= 9780131620179|oclc= 18559256|url-access= registration|url= https://archive.org/details/completemicrowav00gall}} Chapter link is hosted at the Southwest Museum of Engineering, Communication and Computation; [[Glendale, Arizona]].</ref> An early Radarange was installed (and remains) in the galley of the nuclear-powered passenger/cargo ship [[NS Savannah|NS ''Savannah'']]. An early commercial model introduced in 1954 consumed 1.6 kilowatts and sold for US$2,000 to US$3,000 (${{formatnum:{{Inflation|US|2000|1954|r=-3}}}} to ${{formatnum:{{Inflation|US|3000|1954|r=-3}}}} in {{Inflation-year|US}} dollars). Raytheon licensed its technology to the [[Tappan (brand)|Tappan]] Stove company of [[Mansfield, Ohio]] in 1952.<ref>{{cite web|url=https://ohiohistory.wordpress.com/2010/11/02/do-you-remember-your-familys-first-microwave/ |title=Do you remember your family's first microwave? |work=Ohio Historical Society |date=November 2, 2010 |archive-url=https://web.archive.org/web/20160422025448/https://ohiohistory.wordpress.com/2010/11/02/do-you-remember-your-familys-first-microwave/ |archive-date=April 22, 2016 }}</ref> Under contract to Whirlpool, Westinghouse, and other major appliance manufacturers looking to add matching microwave ovens to their conventional oven line, Tappan produced several variations of their built-in model from roughly 1955 to 1960. Due to maintenance (some units were water-cooled), in-built requirement, and cost—US$1,295 (${{formatnum:{{Inflation|US|1295|1955|r=-3}}}} in {{Inflation-year|US}} dollars)—sales were limited.<ref>{{cite web | url=https://spectrum.ieee.org/a-brief-history-of-the-microwave-oven | title=A Brief History of the Microwave Oven }}</ref>

Japan's [[Sharp Corporation]] began manufacturing microwave ovens in 1961. Between 1964 and 1966, Sharp introduced the first microwave oven with a turntable, an alternative means to promote more even heating of food.<ref>{{cite web |title=History of Sharp |url=http://www.sharpusa.com/aboutsharp/companyprofile/sharpandtechnologyhistory.aspx |website=[[Sharp Corporation]] |access-date=June 26, 2018 |language=en}}</ref> In 1965, Raytheon, looking to expand their Radarange technology into the home market, acquired [[Amana (appliances)|Amana]] to provide more manufacturing capability. In 1967, they introduced the first popular home model, the countertop Radarange, at a price of US$495 (${{formatnum:{{Inflation|US|495|1967|r=-3}}}} in {{Inflation-year|US}} dollars). Unlike the Sharp models, a motor driven [[mode stirrer]] in the top of the oven cavity rotated allowing the food to remain stationary.

In the 1960s,{{specify|date=November 2013}} [[Litton Industries|Litton]] bought [[Studebaker]]'s Franklin Manufacturing assets, which had been manufacturing magnetrons and building and selling microwave ovens similar to the Radarange. Litton developed a new configuration of the microwave oven: the short, wide shape that is now common. The magnetron feed was also unique. This resulted in an oven that could survive a no-load condition: an empty microwave oven where there is nothing to absorb the microwaves. The new oven was shown at a [[trade show]] in Chicago,{{citation needed|date=October 2013}} and helped begin a rapid growth of the market for home microwave ovens. Sales volume of 40,000 units for the U.S. industry in 1970 grew to one million by 1975. Market penetration was even faster in Japan, due to a less expensive re-engineered magnetron.
Several other companies joined in the market, and for a time most systems were built by defence contractors, who were most familiar with the magnetron. Litton was particularly well known in the restaurant business.{{Citation needed|date=February 2025}}

=== Residential use ===
[[File:Fiskarsin mikrouuni 1965 (2).jpg|thumb|Finnish [[Fiskars]] microwave from 1965]]
While uncommon today, combination microwave-ranges were offered by major appliance manufacturers through much of the 1970s as a natural progression of the technology. Both Tappan and General Electric offered units that appeared to be conventional stove top/oven ranges, but included microwave capability in the conventional oven cavity. Such ranges were attractive to consumers since both microwave energy and conventional heating elements could be used simultaneously to speed cooking, and there was no loss of countertop space. The proposition was also attractive to manufacturers as the additional component cost could better be absorbed compared with countertop units where pricing was increasingly market-sensitive.{{Citation needed|date=February 2025}}

By 1972, Litton (Litton Atherton Division, Minneapolis) introduced two new microwave ovens, priced at $349 and $399, to tap into the market estimated at $750 million by 1976, according to Robert I Bruder, president of the division.<ref>[https://www.nytimes.com/1972/07/14/archives/litton-introduces-microwave-ovens.html Litton Introduces Microwave Ovens]. [[New York Times]], July 14, 1972, p. 38.</ref> While prices remained high, new features continued to be added to home models. Amana introduced automatic defrost in 1974 on their RR-4D model, and was the first to offer a microprocessor controlled digital control panel in 1975 with their RR-6 model.
[[File:1971rr4.jpg|thumb|1974 Radarange [[RR-4]].
By the late 1970s, technological advances led to rapidly falling prices. Often called "electronic ovens" in the 1960s, the name "microwave oven" later gained currency, and they are now informally called "microwaves".]]

The late 1970s saw an explosion of low-cost countertop models from many major manufacturers.{{Citation needed|date=February 2025}}

Formerly found only in large industrial applications, microwave ovens increasingly became a standard fixture of residential kitchens in [[developed countries]]. By 1986, roughly 25% of households in the U.S. owned a microwave oven, up from only about 1% in 1971;<ref name="CPI_US">{{citation | url = http://www.bls.gov/cpi/cpimwo.htm | title = Hedonic Quality Adjustment Methods For Microwave Ovens In the U.S. CPI | first = Paul R. | last = Liegey | date = October 16, 2001 | access-date = October 5, 2013 | publisher = Bureau of Labor Statistics, United States Department of Labor}}</ref> the U.S. Bureau of Labor Statistics reported that over 90% of American households owned a microwave oven in 1997.<ref name="CPI_US"/><ref>{{citation | last1 = Cox | first1 = W. Michael | last2 = Alm | first2 = Richard | year = 1997 | title = Time Well Spent: The Declining Real Cost of Living in America | publisher = Federal Reserve Bank of Dallas | work = 1997 Annual Report | page = 22 (see Exhibit 8) | url = http://www.dallasfed.org/htm/pubs/pdfs/anreport/arpt97.pdf | access-date = May 8, 2016 | archive-date = October 19, 2004 | archive-url = https://web.archive.org/web/20041019184847/http://www.dallasfed.org/htm/pubs/pdfs/anreport/arpt97.pdf | df = dmy-all }}</ref> In Australia, a 2008 market research study found that 95% of kitchens contained a microwave oven and that 83% of them were used daily.<ref>{{citation | url = http://newsroom.electrolux.com/au/files/2010/01/Westinghouse-How-Australia-Cooks-Report1.pdf | title = The Westinghouse How Australia Cooks Report | date = October 2008 | publisher = Westinghouse | access-date = February 5, 2015 | archive-date = February 5, 2015 | archive-url = https://web.archive.org/web/20150205205537/http://newsroom.electrolux.com/au/files/2010/01/Westinghouse-How-Australia-Cooks-Report1.pdf | url-status = dead }}</ref> In Canada, fewer than 5% of households had a microwave oven in 1979, but more than 88% of households owned one by 1998.<ref>{{cite journal | url = http://www.statcan.gc.ca/pub/11-008-x/11-008-x2000003-eng.pdf | title = Income and expenditures | first = Cara | last = Williams | date =Winter 2000 | number = 59 | journal = Canadian Social Trends — Catalogue No. 11-008 | pages = 7–12 | quote = Microwaves have been adopted even more avidly: in 1979, less than 5% of households had one, but by 1998 over 88% did.}}</ref> In France, 40% of households owned a microwave oven in 1994, but that number had increased to 65% by 2004.<ref>{{citation | url = http://www.freedoniagroup.com/brochure/20xx/2015smwe.pdf | title = World Major Household Appliances: World Industry Study with Forecasts to 2009 & 2014 (Study #2015) | date = January 2006 | at = TABLE VI-5: FRANCE COOKING APPLIANCES SUPPLY & DEMAND (million dollars) | publisher = The Freedonia Group | location = Cleveland, Ohio}}</ref>

Adoption has been slower in [[Developing country|less-developed countries]], as households with disposable income concentrate on more important household appliances like [[refrigerators]] and ovens. In [[India]], for example, only about 5% of households owned a microwave oven in 2013, well behind refrigerators at 31% ownership.<ref>{{cite web | title = Household penetration rate of home appliances in India in 2013 | url = http://www.statista.com/statistics/370635/household-penetration-home-appliances-india/ | access-date = February 5, 2015 | publisher = Statistica}}</ref> However, microwave ovens are gaining popularity. In Russia, for example, the number of households with a microwave oven grew from almost 24% in 2002 to almost 40% in 2008.<ref name=USDA-microwave/> Almost twice as many households in South Africa owned microwave ovens in 2008 (38.7%) as in 2002 (19.8%).<ref name=USDA-microwave/> Microwave oven ownership in Vietnam in 2008 was at 16% of households, versus 30% ownership of refrigerators; this rate was up significantly from 6.7% microwave oven ownership in 2002, with 14% ownership for refrigerators that year.<ref name=USDA-microwave>{{citation | url = http://www.ers.usda.gov/media/612721/householdamenities.xls | archive-url = https://web.archive.org/web/20130626225554/http://www.ers.usda.gov/media/612721/householdamenities.xls | archive-date = June 26, 2013 | format = XLS | title = Ownership of household amenities among selected countries | publisher = Economic Research Service, United States Department of Agriculture | year = 2009 | access-date = February 5, 2015 }}</ref>

Consumer household microwave ovens usually come with a cooking power of between 600 and 1200 watts. Microwave cooking power, also referred to as output wattage, is lower than its input wattage, which is the manufacturer's listed [[power rating]].{{Citation needed|date=February 2025}}

The size of household microwave ovens can vary, but usually have an internal volume of around {{convert|20|L|cuin cuft|sp=us|}}, and external dimensions of approximately {{convert|45|-|60|cm|ftin|abbr=on|}} wide, {{convert|35|-|40|cm|ftin|abbr=on|}} deep and {{convert|25|-|35|cm|ftin|abbr=on|}} tall.<ref>{{Cite web|last=Francis|first=Andrew|date=April 12, 2017|title=Microwave Sizes Comparison|url=https://www.reviewho.com/microwave-sizes-and-dimensions-guide/|access-date=March 10, 2021|website=reviewho.com|language=en}}</ref> Countertop microwaves vary in weight 23 – 45 lbs.<ref>{{Cite web |date=November 17, 2020 |title=How Much Do Microwaves Weigh? Averages from 54 Models |url=https://applianceanalysts.com/microwave-weights/ |access-date=December 17, 2024 |website=ApplianceAnalysts |language=en}}</ref>

Microwaves can be turntable or flatbed. Turntable ovens include a glass plate or tray. Flatbed ones do not include a plate, so they have a flat and wider cavity.<ref name=":1">{{Cite book|last=Williams|first=Alison|url=https://escholarship.org/content/qt3s29h7wd/qt3s29h7wd.pdf|title=Surveys of Microwave Ovens in U.S. Homes|publisher=Lawrence Berkeley National Laboratory|date=December 5, 2012|pages=6, 18 and so on}}</ref><ref>{{Cite journal|last=ANNIS|first=PATTY J.|date=August 1, 1980|title=Design and Use of Domestic Microwave Ovens|journal=Journal of Food Protection|volume=43|issue=8|pages=629–632|doi=10.4315/0362-028X-43.8.629|pmid=30822984|issn=0362-028X|doi-access=free}}</ref><ref name=":2">{{Cite journal|date=July 1, 2016|title=Thawing in a microwave cavity: Comprehensive understanding of inverter and cycled heating|url=https://www.sciencedirect.com/science/article/abs/pii/S0260877416300395|journal=Journal of Food Engineering|language=en|volume=180|pages=87–100|doi=10.1016/j.jfoodeng.2016.02.007|issn=0260-8774|last1=Chen|first1=Fangyuan|last2=Warning|first2=Alexander D.|last3=Datta|first3=Ashim K.|last4=Chen|first4=Xing}}</ref>

By position and type, [[US DOE]] classifies them as (1) [[countertop]] or (2) [[Kitchen stove|over the range]] and built-in (wall oven for a [[Cabinetry|cabinet]] or a [[drawer]] model).<ref name=":1" />

A traditional microwave only has two power output levels, fully on and fully off. Intermediate heat settings are achieved using [[duty cycle|duty-cycle modulation]] and switch between full power and off every few seconds, with more time on for higher settings.{{Citation needed|date=February 2025}}

An inverter type, however, can sustain lower temperatures for a lengthy duration without having to switch itself off and on repeatedly. Apart from offering superior cooking ability, these microwaves are generally more energy-efficient.<ref name=":3">{{Cite journal|last1=Kako|first1=H.|last2=Nakagawa|first2=T.|last3=Narita|first3=R.|date=August 1991|title=Development of compact inverter power supply for microwave oven|url=https://ieeexplore.ieee.org/document/85575|journal=IEEE Transactions on Consumer Electronics|volume=37|issue=3|pages=611–616|doi=10.1109/30.85575|s2cid=108870083 |issn=1558-4127}}</ref><ref name=":2" /><ref name=":4">{{Cite journal|last1=Lee|first1=Min-Ki|last2=Koh|first2=Kang-Hoon|last3=Lee|first3=Hyun--Woo|date=2004|title=A Study on Constant Power Control of Half Bridge Inverter for Microwave Oven|url=https://www.koreascience.or.kr/article/JAKO200411922336424.page|journal=KIEE International Transaction on Electrical Machinery and Energy Conversion Systems|volume=4B|issue=2|pages=73–79|issn=1598-2602}}</ref>

{{As of|2020}}, the majority of countertop microwave ovens (regardless of brand) sold in the United States were manufactured by the [[Midea Group]].<ref>{{cite news |last1=McCabe |first1=Liam |last2=Sullivan |first2=Michael |title=The Best Microwave |url=https://thewirecutter.com/reviews/best-microwave/ |access-date=May 21, 2020 |work=Wirecutter |publisher=The New York Times |date=May 20, 2020}}</ref>

=== Categories ===
[[File:Symbol Microwave oven.svg|thumb|50x50px|Microwave-safe symbol]]
Domestic microwave ovens are typically marked with the microwave-safe symbol, next to the device's approximate IEC 60705 output power rating, in watts (typically either: 600W, 700W, 800W, 900W, 1000W), and a voluntary Heating Category (A-E).<ref>{{Cite web |title=Microwave Fact Sheets |url=https://www.microwaveassociation.org.uk/factsheets/index.php |access-date=March 12, 2023 |website=www.microwaveassociation.org.uk}}</ref>