Pure sine wave inverters output high-quality AC power as good as the grid. For inductive loads such as refrigerators, air conditioners, washing machines, electric lights, electric drills, etc., whose starting power is more than two or three times the rated power, pure sine wave inverters should be used. If you insist on using a relatively poor square wave inverter or a modified sine wave inverter to drive such inductive loads, it will cause serious damage to the load and the inverter.