This paper deals with aspects of the combined power and power (CPP) plants. Such plants consist of two major parts: the steam turbine and gas turbine plants. This study investigates the efficiency of CPP under the effect of several factors. CPP plants including an open cycle gas turbine and a bottoming cycle steam turbine can achieve the highest thermal efficiency obtained with turbomachinery up to date. In this cycle, the anticipated waste thermal energy of the exhaust of gas turbine is used to generate high-pressure steam to empower the steam turbine in the steam cycle. By systematically varying the main design parameters, their influence on the CPP plant can be revealed. A comprehensive parametric study was conducted to measure the influence of the main parameter of the gas and steam cycles on the performance of CPP. The results exhibit that the overall plant thermal efficiency is significantly greater than that of either of the two turbines. Due to the high thermal efficiency, a significant reduction in the greenhouse effect can be achieved. It is found that the regenerative steam cycle will reduce the overall efficiency of the combined cycle. On the other hand, using the reheat steam cycle in the CPP plant will lead to an increase in both the thermal efficiency of the plant and the dryness factor of steam at the exit of the steam turbine.