Automobile exhaust thermoelectric generation technology is an effective way to recover the waste heat from exhaust gas. In order to minimize electricity cost in commercial vehicles (CVs), a hybrid energy system consisting of a thermoelectric generator (TEG), lithium iron phosphate (LiFePO4) battery pack, lead-acid battery pack, and thermoelectric coolers (TECs) is proposed. In addition, an energy management strategy (EMS) based on state machine is developed to satisfy TECs power demand, ensure that the TEG works mostly in the maximum power point tracking (MPPT) mode, and maintain the state of charge (SOC) of the battery within a suitable range under different operating states. The hybrid system model of the CV is constructed with the mathematical model, and then the virtual platform is built to assess the performance of the proposed EMS under the modified Highway Fuel Economy Test (HWFET) driving cycle. A road test is conducted to further verify the reliability of the proposed EMS. The road test results show that the power consumption by TECs is reduced by 45.8% compared with the traditional air conditioner.