An electrically powered trailer refrigeration system comprising: an economized scroll compressor having a discharge port, a suction port, an intermediate pressure stage injection port, and an electric drive motor; a condenser heat exchanger unit having a refrigerant inlet coupled in refrigerant flow communication with the discharge port of said compressor and a refrigerant outlet, and a condenser fan assembly having at least one electric fan motor; an evaporator heat exchanger unit having a refrigerant outlet coupled in refrigerant flow communication with the suction port of said compressor and a refrigerant inlet coupled in refrigerant flow communication with the refrigerant outlet of the condenser heat exchanger, thereby forming a primary refrigerant circuit, and an evaporator fan assembly having at least one electric fan motor; an evaporator expansion device disposed in the primary refrigerant circuit in operative association with the evaporator; an engine driven electric generator for producing A.C. electric current to power the compressor drive motor, the condenser fan motor and the evaporator fan motor; an economizer circuit operatively associated with the economized scroll compressor and in refrigerant flow communication with the intermediate pressure stage injection port of the economized scroll compressor; and a controller for determining a required power to operate the refrigeration system including the compressor drive motor, the condenser fan motor and the evaporator fan motor; wherein the controller selectively opens the economizer circuit and operates the compressor in the economized mode if available power from said engine driven electric generator exceeds the required power for operation of the refrigeration system in the economized mode; wherein the controller selectively closes the economizer circuit and operates the compressor in the non-economized mode if available power from said engine driven electric generator is less than the required power for operation of the refrigeration system in the economized mode. an economized scroll compressor having a discharge port, a suction port, an intermediate pressure stage injection port, and an electric drive motor; a condenser heat exchanger unit having a refrigerant inlet coupled in refrigerant flow communication with the discharge port of said compressor and a refrigerant outlet, and a condenser fan assembly having at least one electric fan motor; an evaporator heat exchanger unit having a refrigerant outlet coupled in refrigerant flow communication with the suction port of said compressor and a refrigerant inlet coupled in refrigerant flow communication with the refrigerant outlet of the condenser heat exchanger, thereby forming a primary refrigerant circuit, and an evaporator fan assembly having at least one electric fan motor; an evaporator expansion device disposed in the primary refrigerant circuit in operative association with the evaporator; an engine driven electric generator for producing A.C. electric current to power the compressor drive motor, the condenser fan motor and the evaporator fan motor; an economizer circuit operatively associated with the economized scroll compressor and in refrigerant flow communication with the intermediate pressure stage injection port of the economized scroll compressor; and a controller for determining a required power to operate the refrigeration system including the compressor drive motor, the condenser fan motor and the evaporator fan motor;