The Best microwave Buying Guide

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1. Microwave Operating Principle

Microwaves vibrate water molecules for rapid heating

Microwave ovens use electromagnetic waves called ‘microwaves’ to heat food. These microwaves pass through most materials except metal but are absorbed by water. As water molecules vibrate, they create friction heat, which warms the food.

Consequently, metal containers can’t be used, and ingredients without moisture won’t heat up.

Faster than other heating methods with less change to food components

Microwaves penetrate food directly, allowing for quicker cooking

Microwave ovens don’t heat by raising the surrounding temperature. Instead, microwaves directly penetrate the food’s internal moisture, resulting in relatively shorter cooking times.

Moreover, since they heat at temperatures below 212°F (100°C), there’s less change to food components compared to high-temperature cooking methods. This makes microwaves suitable for reheating pre-cooked meals or simple dishes like steamed eggs.

However, they struggle with tasks like creating a charred flavor or achieving a crispy exterior with a moist interior.

Uneven heating is common

When cooking with a microwave, some parts of the food may be hot while others remain lukewarm.

This is due to the nature of microwaves, which penetrate differently based on the size and type of ingredients. Typically, they penetrate and vibrate up to about 0.8 to 2.4 inches (2-6 cm).

For example, if the food’s radius is less than 2-2.4 inches (5-6 cm), the center tends to heat more intensely. Conversely, for items with a radius over 5.9 inches (15 cm), the edges often heat more than the center.

Solid foods and thicker items tend to have greater temperature differences compared to foods with high moisture content or thin items. The rotating plate in microwaves aims to reduce uneven heating, but it’s not a complete solution as it only equalizes the contact surface.

For more uniform heating, it’s best to use ingredients with a radius of 3.1-5.1 inches (8-13 cm) or cut larger items into smaller pieces.

The degree of heating also differs depending on the food’s composition.

Foods high in salt, like soups, can become exceptionally hot as salt ions strongly absorb microwaves. Partially thawed frozen foods may heat unevenly, with thawed portions becoming hot while frozen parts remain cold.

Health concerns are mostly myths

Microwaves’ unique operating principle using electromagnetic waves has raised safety concerns. However, most of these are unfounded myths. As long as you don’t stand too close while it’s operating, there’s no need to worry.

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2. Heating Efficiency

Difficult to perceive differences in heating methods
Variations exist based on power output and cavity type

Check the rated output, not power consumption

Microwaves display both power consumption and output in watts (W).

Power consumption represents the actual hourly power usage, while output indicates the microwave’s strength. When purchasing a microwave, focus on the output (rated output).

Most household microwaves have a rated output of about 700W, while high-power models can exceed 1000W.

Performance differences are more significant due to power output
rather than heating method

Manufacturers promote different heating methods like ‘smart inverter’ for energy efficiency, ‘3D heating’ for even cooking, and ‘cooking mirror’ technology. We tested four microwaves to see the actual differences.

Performance differences were more significant with higher power outputs. 1000W models cook about 20-30% faster than 700W models.

For defrosting, each manufacturer has slightly different pre-programmed times. Even with the same output, the power used for defrosting can vary, resulting in slight differences in defrosting levels for the same cooking time.

However, when defrosting for the same duration regardless of programming, higher output models showed noticeably better defrosting performance. Similar to cooking performance, higher output generally means faster defrosting.

In conclusion, since microwaves operate on a simple principle, cooking speed (performance) is similar regardless of the heating method if the output is the same.

No performance difference for ready-to-eat foods

When cooking commonly used items like instant rice, frozen foods, or steamed eggs under the same conditions and time, all were cooked well regardless of power output, with no noticeable taste differences.

While performance differences may exist between products, given that microwaves are mostly used for simple reheating, the perceivable performance difference is minimal. Therefore, you don’t need to worry too much about which product has superior performance when making your choice.

No performance difference for ready-to-eat foods

High-power 1000W models offer less value for money compared to 700W models unless you’re using them frequently or need quick cooking, like in a convenience store setting.

While 1000W models have about 1.3-4 times higher price and power consumption than 700W models, microwave usage times are typically short, around 5 minutes at most, making 700W models sufficient for most users.

‘Flatbed’ microwaves without rotation
Less uniform heating, but acceptable cooking performance

Flatbed types heat without rotation by embedding the microwave emitter in the bottom.

Unlike conventional microwaves, they don’t have a rotating plate (turntable) on the cavity floor, allowing full use of the space.

This makes them useful for heating large, elongated containers or convenience store lunch boxes.

However, the lack of rotation means microwaves are fixed in certain areas, resulting in less uniform cooking compared to rotating types.

Consequently, they may require longer cooking times or manual repositioning of food during cooking.

In tests with 12 products, flatbed microwaves showed performance differences in heating and defrosting compared to rotating types.

However, when cooking ready-to-eat foods under the same conditions as rotating types, all products cooked normally and tastily, with no undercooked or unheated items.

Yet, there are quite a few performance issues compared to conventional rotating microwaves, such as “cheese not melting when heating pizza,” “only the bottom of hot dogs getting heated,” or “taking much longer to defrost frozen rice compared to existing microwaves.”

Therefore, if you want quick cooking, it’s better to buy a rotating type. If you frequently use various shaped containers and don’t mind the time, flatbed types can be much more convenient.