A method for operating a refrigeration system for a mobile unit includes steps of: 1) providing a refrigeration unit having a compressor, an evaporator, and at least one fan operable to move air towards the evaporator, a generator dedicated to the refrigeration unit, and a battery; 2) determining at least one environmental parameter in one or both of the mobile unit and the refrigeration unit; and 3) selectively operating the refrigeration unit in one of a plurality of modes based on the environmental parameter. The plurality of modes includes a first mode wherein at least the fan is powered by the battery, and a second mode wherein the compressor and the fan are powered by the generator.