Where will you put the microwave? Countertop microwave ovens are the cheapest option, but they take up precious counter space. An over the range microwave will save space, but it's more work to install, and experts say it won't do as good a job of venting heat and fumes as a real range hood. A built-in microwave, which installs against a wall, leaves room for a range hood and leaves your counters clear, but it's by far the priciest option. Many users say a better option is to build a shelf for a countertop microwave oven to sit on; adding an optional trim kit can give it the look of a built-in. Regardless of which option you choose, be sure to measure your space carefully so you know how big a microwave you can handle. Don't forget to allow space on the left for the door swing (virtually every microwave on the market opens from the right).
How will you use it most often? 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. However, these features can add to the cost, so don't invest in a model loaded with features you're unlikely to use. For instance, a convection feature, which enables a microwave to bake and brown like a normal oven, will add at least $100 to the cost of a microwave, so it's only worthwhile if you really need a second oven. Instead, look for shortcut keys for the settings you'll use most often, whether that means melting butter or reheating coffee.
How much room do you need? If you want to cook or reheat large dishes, pay careful attention to capacity -- not just the stated capacity, but the usable space inside. Some shoppers go so far as to bring a large platter to the store when shopping to make sure it will fit inside.
How much noise can you handle? The good news is that most modern microwaves are pretty quiet. In the professional sources we consulted, we didn't find any that were given a low rating for their noise level. However, even models that the experts rate as quiet sometimes provoke complaints from owners about their loudness. If possible, try to listen to the microwave running in the store and judge for yourself whether its sound level is something you can live with.
Having your microwave break down right after the warranty expires is frustrating, but having it break down within the warranty period can be an even bigger hassle. Many owners complain about having to drive their microwave ovens 100 miles or more to get them serviced. To avoid this problem, check the manufacturer's website before you buy a particular microwave and find out where your nearest repair shop is. Also, be aware that some manufacturers require the product to be in its original packaging, with the original sales receipt. So don't discard these items without checking your warranty first.