In the present paper the efficiency of thermoelectric generators for different types of combustion engines was analyzed. Modeling of thermal flows through the thermoelectric generator and its output parameters at different placement from output collector of a standard and heat-insulated diesel engine was carried out. As the consequence, the perspective of the thermoelectric generators usage for heat-insulated combustion engines was shown. Thermoelectric generator for heat-insulated engine has similar physical specifications and several times as large power as compared with conventional engine. The possibility of reaching the efficiency up to 10 % of the thermoelectric generators in heat-insulated engines by augmentation of heat transmission from exhaust to the junctures of thermoelectric battery was shown.