Accurate measurement of efficiency for a thermoelectric generator (TEG) is of great importance for materials research and development. Approximately all the parameters of a thermoelectric material (TEM) are temperature dependent, and so we cannot directly apply the η max formula for efficiency calculation in the large temperature range. In this work, we have calculated TEG efficiency, and we study the suitability of different TEMs like Bi 2 Te 3, Sb 2 Te 3, PbTe, TAGS ((AgSbTe 2)0.15(GeTe)0.85), CeFe 4 Sb 12, SiGe, and TiO 1.1 in the estimation of TEG efficiency. The efficiency of TEG made up of Bi 2 Te 3 or Sb 2 Te 3 gives ～7% in the temperature range of 310?K–500?K. PbTe or TAGS or CeFe 4 Sb 12 generates ～6% in the temperature range of 500?K–900?K and SiGe or TiO 1.1 also have remarkable efficiency in the higher temperature range, i.e., ～1200?K. The calculated efficiency obtained is close to experimental results. Here, we report the enhancement of efficiency by using the segmented technique for different combinations of the above-mentioned materials. To this end, the proposed values of overall efficiency of TEG by segmenting Bi 2 Te 3 and PbTe; Bi 2 Te 3 and TAGS; Bi 2 Te 3 and CeFe 4 Sb 12 are 12%, 14%, and 11.88%, respectively, for the temperature range of 310?K–900?K. For automobiles, the efficiency of TEG having fixed exhaust temperature with varying sink temperature is also discussed. For the steel industry and spacecraft applications (up to 1200?K), either segmentation is done by comprising Bi 2 Te 3, PbTe and SiGe, or Bi 2 Te 3 and TiO 1.1, which yields an efficiency of ～15.2% and ～17.2%, respectively. The relative change in efficiency by considering loss at the interface surface is found to be 10.5%. The proposed methodology and results can be treated as a viable option for engineers who are looking to fabricate TEG in real life by using the temperature dependent material's parameters such as thermal conductivity, electrical conductivity, and Seebeck coefficient on which z T ˉ depends.