We describe an exergy analysis for thermoelectric (TE) generators used as a topping cycle on top of Rankine cycle steam turbines. The TE generators are stilized to effectively convert the available heat at higher temperature than the temperature range the steam turbine uses in current power plants. The destroyed exergy flow by adding TE generators are a function of the thermal resistances. The balance between the TE power generation and the available energy for the bottoming cycle needs to be considered. We also investigate the performance per investment cost [W/$] for the topping. TE generator and the waste heat recovery TE as a comparison. Higher exergy utilization with the thermal resistance across the boiler wall improves the system efficiency by approximately 6%. Adding the topping cycle results in relatively better efficiency but significantly lower cost compared to the waste heat recovery of the flue gas of the boiler.