Consider form, function when choosing microwave

In the market for a new microwave oven? The latest models are smaller and sleeker than their predecessors, and they do a lot more, too. Touchpads preset to the right cooking times and temperatures let you bake potatoes and cook frozen pizza at the touch of a finger. Many brands allow you to put something in the microwave, then program cooking to start hours later.

But deciding which oven is right for you depends on form (where you’re putting it) and function (what you need it for).

Need to know: Microwave ovens use radio waves to agitate the molecules in food, thereby heating it (the temperature inside the oven doesn’t change). The thicker the food, the longer it takes to cook. So if you’ll be using the microwave for primary meal preparation for a family, you’ll need a larger, higher-powered unit. For reheating takeout, a small unit will suffice.

Cooking compartments range from 0.7 cubic foot, the size of a dinner plate, to 2.1 cubic feet, big enough for a large casserole dish or for heating several things at once.

Bad advice: “Avoid microwaves with overly complex control pads that offer to cook foods you never eat.” Take all the help you can get. Left on your own, you’d spend more time on trial-and-error programming than on cooking. (See below.)

Jargon alert: A microwave oven’s power is measured in watts. Full-size microwaves (larger than 1.2 cubic feet) are available from 650 to 1,000 watts. Intermediates (0.8 to 1.1 cubic feet) have 600 to 800 watts. Compact units (less than 0.8 cubic foot) range from 500 to 700 watts.

Most cooking times listed on food packages or with recipes are based on a 600-watt oven. Ovens with higher wattage cook food faster than ovens with lower wattage, so you may need to adjust cooking times — food that takes six minutes to cook in a 600-watt oven might take only five in a 700-watt model. Before you buy, be realistic about the power you need.

Be sure to ask: Does the microwave have a moisture sensor, which allows for more accurate cooking? The sensor measures both temperature and moisture levels in the food. When the food is heated enough that it steams, the sensor can determine how much longer it should cook, based on how long it took to reach the steam stage. You insert the sensor in the food, and it registers automatically on the microwave’s touchpad — the oven will go off when the food is done.

Good advice: Don’t buy a combined microwave/convection oven, with a fan that constantly forces heat around the food and allows for roasting and baking, if your regular oven can switch over to convection cooking. Combo models are pricier — at least $250 more.

What it will cost: Countertop microwaves range from $40 to $250, depending on size and wattage; over-the-range and wall-mounted models cost from $150 to $500, because they tend to be a bit larger. Some countertop microwaves have built-in toasters; they cost about $150. These have been available for only a couple of years, so it’s still unclear whether the microwaves outlive the toasters or vice versa.