There are two basic decisions to make when choosing microwave oven: size and power.

Capacity: The size, measured in cubic feet, refers to the dimensions of the cooking chamber, not the exterior dimensions of the unit. Most small ovens are suitable for very limited use, offering chamber capacities of .3 to .5 cubic feet. Consider these if counter space is at a premium and your general use is heating drinks, small thawing jobs, or the occasional TV dinner. The medium- size oven has become the most popular. Offering chamber sizes of .6 to .8 cubic feet and a trimmed down exterior dimension, you get the best of versatility and counter space. This size also provides more of the programming niceties which can improve the usefulness of the microwave as a bona fide cooking tool. Large sizes, .9 cubic foot and more, can handle most any cooking load but generally occupy significantly more counter space and may be more than the average consumer will ever use.

Power: Power and size generally go hand in hand. Small ovens range from 500 to 650 watts, medium ovens from 600 to 800 watts and large ovens from 700 to 900 watts. This variation in cooking power can significantly affect cooking time, the higher powered models cooking nearly a third faster than the low-powered units. Also, most recipes are calculated with cooking times based on high power. Whatever size works for your kitchen, select the highest power available.

Features

Carousel: Most ovens come with a rotating carousel that improves distribution of heat and eliminates the need to stop the cooking process to rotate the food. The carousel does, however, use up some of the cooking chamber space. For the best of both worlds, look for a carousel that is removable or recessed.

Convection Oven: Combining a convection oven with the microwave is one of the many attempts to overcome the technology's prime deficiency, lack of browning, and it works. With this combination, while the microwaves do their thing, generating heat inside the food, a fan circulates heated air over the outside of the food allowing it to brown and crisp. This feature can usually be switched on or off as needed. As a serious alternative to the conventional oven, the convection/microwave combination is a must.

Electronic Keypad: The knobs are gone for the most part and the touch-sensitive pad reigns supreme. Make sure you can read it and use it. Look for large, well-lit numbers and read-outs. No matter how sophisticated the available programming, make sure it has one-touch or two-touch cooking options (the ones you'll use the most). Preset buttons for popular foods like popcorn, tea, or hot dogs are very handy.

Temperature Probes: This electronic meat thermometer tells the microwave when the temperature inside the food is correct and causes the unit to power down or shut off. Unfortunately, this device is the most useful on the types of food for which the microwave is least suitable: roasts, turkeys, etc.

Auto Defrost: Microwaves do not generate heat evenly in food, so defrosting is a balancing act between applying enough heat to defrost and not applying so much as to cook the most heated parts. Auto defrost allows the unit to alternate power levels or go into no power mode for brief periods, allowing the heat to equalize and defrost the food evenly. This feature is extremely convenient but maddeningly slow.

Clean-Up: Microwaves get messy. You will have boil-overs and spills. Look for a smooth interior and a design that will keep spills on the inside when you open the door.