A significant contribution towards climate change and global warming is the residual thermal energy generated from automobiles as exhaust gases in IC engine-based vehicles and from batteries and fuel cell heating in green vehicles. This waste heat, also known as thermal energy, has the potential to be transformed into valuable electrical energy through the utilization of a thermo-electric generator (TEG). The performance of the TEG depends on various parameters such as material properties, geometries (form factor), and operating conditions. Current research focuses on the effect of the form factor, i.e., the semiconductor’s length, width, and height (thermocouple), on the overall performance of the TEG. Eleven cases are examined by varying the length, width, and height of the thermocouple. The TEG’s performance is measured using its internal resistance, open circuit voltage, maximum current, output power, and efficiency. Current work reveals that there is a significant impact on TEG’s performance due to changes in the height of the thermocouple when compared to changes in the length and width of the thermocouple.