How many amps are needed to efficiently run a refrigerator?

If you are talking about a certain kind or brand, look at the label inside the door. The label will tell you how many amps this unit will need. However all residential refrigerators will run on a 15 amp dedicated circuit or be fine plugged into a regular 20 amp appliance circuit (which is required in kitchens). I have a large side by side unit and it only draws 6.6 amps max. Note that the starting current of an induction motor will be higher, of course, but will drop and stabilize at a "nominal" level within seconds.