This is one key fact you have to look into when selecting or purchasing a Microwave oven. The size of your microwave affects the Location of the Microwave oven. If you are planning on placing the microwave in a small space, small kitchen, or in a dorm room, you will need a smaller microwave, which will result in lower wattage.  However, if you are installing or replacing an over-the-range microwave, usually those spaces are wider and result in higher wattage.