Parabolic Trough Concentrating Solar-thermal Power (CSP) technology represents one of the most promising options among available CSP systems for generating renewable electricity at utility scale. Within geographical boundaries of the Islamic Republic of Iran, there are a large number of potential sites with solar insolation levels around 1800kwh/mˆ2.yr. The power plant complex in Yazd (a city in middle of Iran) is selected as a study site. Two computational codes are used for modeling of different configurations of solar power plants. These are the Pilksolar's performance model and Fichtner's cycle process calculation software. In this article two plant configurations are considered. They are the standalone solar electricity generating system (SEGS). And, integrating a solar field into a combined cycle plant, the Integrating Solar combined cycle System (ISCCS). Performance calculations for these configurations are carried out and a comparison between the methods is made. It shows that integrating solar plants into the Iranian grid may be considered as an action to counter production losses from the gas turbines due to high summer ambient temperatures.