In this paper a unified model of a solar electric generation system (SEGS) is developed using a thermo-hydrodynamic model of a trough collector combined with a model of a traditional steam power-house. The model evaluates thermal properties, steam flow rate and pressure drop in a direct steam generation (DSG) or an oil based collector field. The SEGS's performance in different collector field power-house arrangements is evaluated. Long term performance is implemented by integrating the unified model in TRNSYS using hourly radiation data from the currently operating SEGS site in California. The performance of SEGS under Jordanian radiation conditions is studied by evaluating the yearly delivered energy from a collector field at different sites. (C) 2002 Elsevier Science Ltd. All rights reserved.