Proper use of a microwave increases its efficiency. How many amps microwaves will use does vary based on the make, model, and the location. To determine the amps, you will need to take the watts and divide it by the volts. A microwave will typically have the power in watts located somewhere on the appliance. In the United States, voltage is typically approximately 120. So, for a microwave with a wattage of 1200 it is expected that it should deliver about 10 amps.