Microwave ovens don’t actually deliver heat to a food item the way a conventional oven does (via heated air); they work by using microwave energy to cause the water and other simple molecules in food to rapidly vibrate, which generates internal friction at the molecular level, heating the food from within. That’s why microwave ovens can heat things so quickly, and why they’re so good at steaming vegetables in their own juices—they don’t rely on the slow and uneven process of transferring heat energy from the air, the way a conventional oven does. But the microwaves aren’t delivered evenly, the way heated air in a conventional oven is. That’s why microwave trays rotate: so that, ideally, every section of the food item gets equal treatment. But the world doesn’t operate on ideals, and neither do microwave ovens. Almost inevitably, you’ll get hotter spots near the center of the oven, which may or may not matter depending on the size of the thing you’re microwaving.
Spinach retains nearly all its folate when cooked in a microwave; in comparison, it loses about 77% when boiled, leaching out nutrients. Bacon cooked by microwave has significantly lower levels of carcinogenic nitrosamines than conventionally cooked bacon.[44] Steamed vegetables tend to maintain more nutrients when microwaved than when cooked on a stovetop.[44] Microwave blanching is 3–4 times more effective than boiled water blanching in the retaining of the water-soluble vitamins folic acid, thiamin and riboflavin, with the exception of ascorbic acid, of which 28.8% is lost (vs. 16% with boiled water blanching).[47]
The 1.2-cubic-foot Toshiba didn’t heat as evenly as the smaller Toshiba. Unlike the 0.9-cubic-foot version, this Toshiba uses a steam and temperature sensor to automatically determine cooking time. However, we didn’t find the sensor particularly accurate: The baked potato we cooked using it came out completely raw in the center. In our heat map test, the marshmallows near the center of the turntable came out very dark. That said, it heated more evenly across the surface of the turntable than most of the microwaves we tested. The popcorn we made wasn’t burned, though it did have twice as many unpopped kernels as the 0.9-cubic-foot model. We liked that this model beeps to prompt you to flip meat while defrosting, something the smaller one doesn’t do. Impressively, this Toshiba only slightly cooked the edges of ground beef on the defrost mode, unlike most of the models we tested, which fully cooked entire sections of meat.
Japan's Sharp Corporation began manufacturing microwave ovens in 1961. Between 1964 and 1966, Sharp introduced the first microwave oven with a turntable, a feature that promotes convenient even heating of food.[16] In 1965, Raytheon acquired Amana. In 1967, they introduced the first popular home model, the countertop Radarange, at a price of US$495 ($4,000 in 2018 dollars).
Ever wondered how microwaves heat up food so quickly and efficiently? These appliances contain a part called a magnetron, which uses electricity to create high-powered radio waves. The waves are pushed into the microwave’s interior, where they bounce off the metal walls and penetrate whatever food you’re cooking. The turntable spins to help the waves hit the food from all angles, and this process makes the molecules in the food vibrate, warming them up. However, one of the downsides of microwave cooking is that radio waves can only travel a few centimeters into your food, so larger items don’t always cook evenly.

This mistake can happen when buyers get a little too excited. When all you’re focused on is, “When did the microwave come out?” and “Does it have the latest features?”, then you’re ignoring how you currently use microwaves, which is just as important. If you don’t use any of those menu buttons or defrost features now, you probably won’t use them on a new microwave, either. Buy microwaves based on how you like to use them, not on the latest flashy features.
For convenience in the kitchen, nothing beats the microwave, which allows you to cook and reheat food from the inside out. After more than 100 hours of research and testing, we think that the Toshiba EM925A5A-BS is the best microwave for most kitchen counters. It’s easy to operate, has a number of express cooking options that heat food quickly and evenly, and even has a mute button so you can cook in silence.
And let’s not forget about design! Today’s microwaves come in sleek, stainless steel frames that will look great in your kitchen and match your other appliances well. Microwave doors are easier to open, too. And if your current microwave is a little too small on the inside for your plates or cups, you can always upgrade to more cubic feet of space so you can use the dish of your choice! These microwaves cook your food better than ever.
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-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).[5] 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.