To improve the power output and efficiency of the thermoelectric generator system, the variation in the thermoelectric leg configuration is another option. In this paper, the thermodynamic analysis of exore-versible thermoelectric generator including influence of Thomson effect as well as influence of leg geometry on the power output and efficiency of the device has been carried out. The modified expressions for dimensionless figure of merit, power output, irreversibilities, energy and exergy efficiency considering Thomson effect have been derived analytically. The effects of various parameters such as dimensionless temperature ratio (theta), shape parameter (R-A), Thomson effect and load resistance ratio (R-L/R-0) on the power output, energy and exergy efficiency have been studied. The operating range for shape parameter has been found which improves the power output, energy and exergy efficiency of the device, however, the optimum operating point corresponding to maximum power output is different from that of the maximum energy and exergy efficiency. The results of this study shows that when the shape parameter is increased from 1 (flat plate TEG) to 2 (trapezoidal TEG), then the energy and exergy efficiency improve by 2.32% and 2.31% respectively with a 1.3% decrease in power output at R-l/R-0 = 10 and theta = 0.5. This study will help in designing of the improved thermoelectric generator systems for different leg geometries. (C) 2017 Elsevier Ltd. All rights reserved.