Renewable energy sources and especially solar energy may be the answer to the increasing demand for energy, leading to the reduction of fossil fuel consumption and its associated negative environmental impact. An attractive solution to this problem could be the combination of renewable and conventional energy sources technologies such as the integrated solar combined cycle power plants (ISCCP). In this paper the operation of a 50 MW ISCCP with natural gas and parabolic trough solar collectors was simulated using TRNSYS software. The proposed power plant performance, fuel consumption and solar contribution were analyzed through six different simulation scenarios for different collector area. Two different modes of operation, namely power boost and fuel saving, were considered. Also, an economic analysis shows the optimal contribution rate of solar field taking into consideration the results of various simulation scenarios. (C) 2013 Elsevier Ltd. All rights reserved.