A transportation refrigeration unit TRU (26) and power system. The TRU (26) and power system including a compressor (58) configured to compress a refrigerant, an evaporator heat exchanger (76) operatively coupled to the compressor (58), and an evaporator fan (98) configured to provide return airflow and flow the return airflow over the evaporator heat exchanger (76). The system also includes a return air temperature RAT sensor (142) disposed in the return airflow and configured measure the temperature of the return airflow, a TRU controller (82) operably connected to the RAT sensor (142) and configured to execute a process to determine an AC power requirement for the TRU (26) based on at least the RAT (142), a generator power converter (164a) configured to provide a second DC power (165b), an energy storage system (150) configured to receive the second DC power (165) and provide a three phase AC power (157) to a power management system (124).