Window AC units have two watt ratings: starting wattage and running wattage. Starting wattage is higher because as the machine starts up and the motor begins to turn, amperage spikes as the motor draws higher current to overcome inertia and starting friction. A typical starting wattage for a window unit is 2200. Once the motor is running steadily, the amperage drops and the wattage usually is around 1500. Your unit may have different ratings. Examine the nameplate or the specifications in the manual to determine how much power your AC unit uses.