All portable generators have performance requirements for wattage output. First, the listed maximum wattage is listed on the tag. Second, the generator is run with no appliance plugged in. Little by little, appliances are added until the maximum wattage is reached. careful measurements are taken. The wattage outputs are carefully recorded and engineering equations are used to interpret the data. The generator is in compliance if the actual wattage output is at least 90 percent of the manufacturer's stated wattage on the tag.
For an appliance to function correctly, it has to have a constant 120 volts at the plug. For a generator to be in compliance, its output has to be within 10 percent of the stated voltage on the tag. Therefore, the generator has to provide anywhere from 108 volts to 132 volts for it to be within tolerance. This has to be for all load conditions.
AC means alternating current. Utility power is 60 hertz, meaning the electrical waves arrive at 60 times per second. A generator must duplicate utility frequency. For generators to be in compliance, they cannot be more than 5 percent off on the frequency. Therefore, the frequency has to be between 57 to 63 hertz. If the generator wanders beyond these figures, it is not in performance compliance.