Most of solar systems present several operational restrictions, making it necessary to include an energy buffer and, usually, a secondary or backup energy source. The inclusion or exclusion of these elements during solar system operation produces changes in the energy which feeds the main process, resulting in changes in the process dynamics. For this reason, adequate tools to both analyze and predict the continuous system behavior must be available in order to maximize the benefits of applying a solar system and to model the changes of the main energy sources (dictated by discrete signals). In this context, hybrid modeling is selected since it fits the main operational objectives of solar thermal plants. In this work, several subsystems: a thermal flat-solar collector field, a hot water accumulation system, and a gas heater, which make up a thermal solar system, are modeled based on first-principle equations. Then, the discrete dynamics are also included in order to develop a hybrid model of the whole solar system. The resultant hybrid model is able to simulate the different configuration modes of the solar system, being highly useful for both simulation and control design purposes. (C) 2013 Elsevier Ltd. All rights reserved.