Numerical simulation was performed to study the TEG utilization to recover waste heat from condenser of air conditioning system. The Thermal-Electric module in the ANSYS software is used to perform 3D numerical simulation in this study. The thermoelectric couple series incorporated with external load are setup in the simulation domain. Influence of temperature difference between hot and cold side on the power output is investigated. Behaviors of main electric parameters such as voltage, electric current, and power output in the model are examined. Moreover, optimizing the maximum power output as a function of load resistance respect to temperature difference are studied. The small generated power from TEG can be used to sensor power in household, especially, to check the water level and to detect gas leak, etc.