Energy needs and awareness of renewable energy are always increasing from year to year. This results in a very large demand for renewable energy. Nowadays, its special concern is exhaust emissions. This article presents numerical thermoelectric modeling and simulation with BiTe-based materials. The type of sandwich material and the height of the thermoelectric legs are varied for the output power and power efficiency factor. Numerical simulations are carried out using software assistance. The input temperature on the thermoelectric hot side varied from 300-1000K. A simplification of the simulation was carried out by taking into account thermoelectricity with a single leg (a couple n-type and p-type). Based on the analysis, the choice of sandwich material has an effect on the temperature gradient and the output power of the BiTe-based thermoelectric generator. The resulting power output is 32.82 mW, and the maximum efficiency is 22.92% when the temperature difference is 350–400 K. The results show that the developed generator can be used at temperatures below 600K.