Thermal energy from different sources can be converted into electricity by using thermoelectric modules. Controlling the temperature uniformity over the heat spreader of the thermoelectric power generation system is a critical issue for its performance. In this study, we compared the outputs of the thermoelectric power generation system which has uniform temperature distribution with that without uniform temperature distribution over the heat spreader. The model in which thermoelectric materials are temperature related was developed. Finite element based software with thermal-electrical multi-physics coupled was employed to simulate the system. In addition to the simulation, we performed experimental activities. In the simulation and experimental activities, electric current output, power output, open circuit voltage and the efficiency of the system in the cases of uniform and non-uniform temperature distribution over the heat spreader are evaluated. The simulation and experimental results show that the uniform temperature distribution over the heat spreader gives better outputs than the non-uniform temperature distribution. (C) 2013 Elsevier Ltd. All rights reserved.