Over-the-Range MicrowaveWhat it is: In over-the-range microwaves, the microwave and range hood are one unit. Some of these units vent, while others only recirculate air. These units are around 24 to 30 inches wide and are shallower than full-size built-in microwaves. The shallow size means they can be installed above the cooking surface without causing you to hit your head every time you lean forward to mix the tomato sauce.Variations: Most of these microwaves are designed to go over a 30-inch range or cooktop and may come with trim pieces to make them look wider. Recirculation and vented options are both available. If it's a vented model, check the wattage and CFMs (cubic feet per minute) on the hood to make sure you're getting the right one for your needs. When to use: If you're limited on space in your kitchen, this is a good bet. Stylewise, it tends to looks better in an apartment or condo than a single-family home. If you've got the space, I recommend installing a stand-alone exhaust fan or hood and putting the microwave in another location. From a design perspective, hoods command a presence and look more substantial over a range than a microwave-hood combo. Plus, microwave-hood combos are often not as powerful, since they have lower CFMs. The same is true of recirculating hoods, which have charcoal filters and don't actually vent to the exterior.