Does the NEC specify what is required to operate a microwave oven - the kind that is mounted permanently in a cabinet, and the smaller kind found on countertops?
NEC 110.3.B says “equipment shall be installed and used in accordance with any instructions included in the listing or labeling.”
I recently purchased a small countertop unit. Rated Power Consumption 1000 watts.
The manual says “For safety purposes this oven must be plugged into a 15 amp circuit. No other electrical appliances or lighting circuits should be on this line.” Then it says “Your microwave oven can easily be placed in your kitchen, family room or any other room in your home.” I contacted them to ask about the discrepancy (How can you easily move an appliance to any room if it requires a dedicated circuit?), but their final comment was simply “I'm sorry you are unhappy with our recomendations. It would be safer, therefore preferable to use a grounded receptacle with the unit. GFCI would provide adequate grounding.”
If a microwave oven rated at 1000 watts needs a dedicated circuit, what about the toaster rated at 1600 watts, and the clothes iron rated at 1200 watts? What does the NEC specify (if anything) about these appliances found in most houses?

Microwave Oven Requirements