Three factors shoppers must bear in mind when choosing a microwave oven are type, size and features. Microwaves are available as a countertop, over-the-range or built-in. Countertop microwaves, the most popular option, are typically the least expensive and don't require complicated installation. However, they do take up quite a bit of counter space. Over-the-range microwaves, which eliminate this problem, include extra fans for venting heat from a range. However, experts caution that they don't do this job as well as a fume hood that extends over the full range top.

Over-the-range microwaves are generally more expensive than traditional countertop units. They're also more complicated to install because they're heavier and require a dedicated electrical outlet and an outside vent in the area where it will be installed. While some experienced do-it-yourselfers successfully install their own over-the-range microwaves, experts say most individuals should enlist the help of a professional. The same goes for built-in microwaves, which are installed either within a custom-built cabinet or over a counter. These models leave counter space clear and leave the area over the stove open for a range hood. However, built-in microwaves are the most expensive type. Typically, these units are added to a kitchen during a remodel or as a replacement for an existing built-in. We do not cover built-in microwaves in this report.

Microwaves are available in a variety of sizes. Full-size microwaves (1.5 cubic feet or larger) can accommodate large dishes, such as casseroles and lasagnas. Midsized microwaves usually have capacities of around 1.2 cubic feet, and compact microwaves may be as small as 0.5 cubic feet. Although smaller microwaves require less counter space, they also offer less cooking power. Large microwaves usually have cooking power of around 1,200 watts, while compact microwaves typically measure around 800 watts. Microwaves with lower power require longer cooking times and may not heat food as evenly. However, experts say differences of around 100 watts are not significant.

Here are some other features you should consider when buying a microwave:

  • Check for a cooking sensor. Cooking sensors, which measure humidity in the microwave and automatically adjust cooking times, can help prevent overcooking. While most new microwaves have cooking sensors, some budget models do not.
  • Inverter technology isn't essential. Some microwaves use inverter technology to cook food more evenly. Most microwaves, when cooking at half power, cycle between periods of 100 percent and no heat. Inverter microwaves, on the other hand, can cook at 50 percent for the entire period. Reviewers say this technology does improve cooking performance, but we found plenty of good reviews for microwaves without this feature.
  • Look for a turntable. Microwaves are not inherently good at heating foods evenly. That's because the heating waves only penetrate a certain depth beyond the surface of the food. Microwaves with turntables help prevent cold middles by rotating food to provide more even heat exposure. An alternative to a turntable is a rectangular tray that slides from side to side. These trays can accommodate larger dishes that might not fit on a round carousel.
  • Convection ovens can be costly. Some microwaves double as a convection oven, which uses currents of hot air to cook and brown food. Typically, you'll pay at least $100 to $200 more for a microwave with this feature. However, experts say most convection microwaves won't produce the same results as a regular oven.
  • Shortcut keys save time. In addition to the ever-popular popcorn setting, many microwaves now feature one-touch cooking for soup, oatmeal and a variety of other foods. Automatic settings for reheating and defrosting are also common.
  • Nearly every microwave oven on the market opens from the right. We saw only one model--the Kenmore 8852--that's outfitted with a dual-swing door, so it can open from either side.

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