Parabolic trough power plants are currently the most commercial systems for electricity generation. In this study, a transient numerical simulation of a solar power plant was developed by using direct steam generation (DSG) technology. In this system, condensate water from a Rankine cycle is pumped directly to solar parabolic trough collectors. The pressurized water is heated and evaporated before being superheated inside the solar collectors and directed back to the steam turbines, where the Rankine cycle is a reheated-regenerative cycle. The plant performance with saturated steam production is compared with the performance of a superheated plant. A mathematical model of each system component is presented, with the solar power cycle modeled by the TRNSYS-17 simulation program. Annual transient performance, including plant power and efficiency, is presented for both plants. As expected, the power of the superheated plant outperforms the saturated plant by approximately 45%, whereas the efficiency decreases by approximately 10%. Furthermore, the power of such plants is considerably improved under the weather of Makkah, 22.4 degrees N, and it is approximately 40MW for both the spring and autumn seasons. The annual generated energy is approximately 8062 MWh. The levelized electricity cost (LEC) was estimated for both the DSG and the corresponding synthetic oil plants. The DSG plant has an approximately 3% higher LEC than a synthetic oil plant with heat storage and an approximately 11.2% lower LEC than an oil plant if the plant has no storage. Copyright (C) 2016 John Wiley & Sons, Ltd.