Recommended for 110v appliances rated equal or less than at 3571 watt ( motor driven) or 4000 watt (no motor). Perfect for powering refrigerators, freezers, air conditioners, and other compressor-driven appliances up to 3,571 watts, as well as all other non compressor household and office appliances rated up to 4,000 watts . Convert 110V, is that compressor and motor driven appliances have fluctuating loads ( example-surge on startup) and the suggested recommended maximum watts, allows for this fluctuation.