Combined cycle power plants (CCPP) are increasingly important for safer and cleaner electricity generation. In this context it is imperative to explore options to enhance its thermal performance for its design and off-design condition. This study presents the performance comparison of two heavy-duty gas turbined (GT) based CCPP with triple pressure steam bottoming cycle. The CCPP system component is modeled using a commercial software Ebsilon and the off-design performance prediction is made using necessary component correlations. The correlations make use of normalized curves that are generated from model runs and apply the factors received from such curve to design performance to estimate the off-design performance. The model simulation is validated against literatures. Furthermore, inlet air cooling technique (IAC) is introduced in this study to enhance the CCPP power production without compromising component performance. The performance comparison of both the CCPP units are presented in an integrated manner by considering interaction of bottoming cycle on GT operation. The results are established as a function of ambient temperature based on energy and exergy principle and the power boosting and economic profit. The results also demonstrate the benefit of IAC on part-load performance. The component level exergy analysis proved that IAC improves the system exergy efficiency.