Recent advances in thermoelectric technology have made exhaust-based thermoelectric generators (TEGs) promising for recovery of waste heat. Utilization of exhaust-based TEGs in heavy-duty vehicles was studied in this work. Given that the generated power is limited, the alternator is still indispensable. To improve the fuel economy, the generated electricity must be integrated into the automotive electrical system and consumed by electrical loads. Therefore, two feasible ways of integrating the generated electricity into the automotive electrical system are discussed: one in which the original alternator works only under certain conditions, i.e., the "thermostat" strategy, and another in which a smaller alternator is adopted and works together with the TEG, i.e., the "cooperative work" strategy. The overall performance and efficiency are obtained through simulation analysis. The simulation results show that both methods can improve the fuel economy, but the former provides better results. Moreover, if the electrical loads can be properly modified, the fuel economy is further improved. These simulation results lay a solid foundation for application of TEGs in vehicles in the future.