A transportation refrigeration unit (TRU) system is provided and includes a damper assembly configured to direct air flows through first or second pathways and an evaporator disposed in the first pathway, a coil element surrounded by phase change material (PCM) and disposed in the second pathway and a routing assembly configured to direct refrigerant through the evaporator or the coil element. With the PCM pre-cooled, the damper and routing assemblies are controllable to respectively direct the air flows through the first pathway and the refrigerant through the evaporator when first conditions are met and to respectively direct the air flows through the second pathway when second conditions are met.