In this paper, a RSORC (regenerative solar organic rankine cycle) is optimized. For this purpose, hourly analysis is considered and evaporator pressure, condenser pressure, refrigerant mass flow rate, number of solar panel (solar collector), storage capacity and regenerator effectiveness are selected as design parameters. Then RPGA (Real Parameter Genetic Algorithm) is used to find the maximum value of a new objective function named the RAB (relative annual benefit). The optimization is separately performed for three working fluids including R123, R245fa and isobutane. The optimization results reveal that the best studied working fluid is isobutane with 258810 $/year as relative annual benefit and follow by R245fa and R123 with 68173 and 64028 $/year as the RAB. The hourly analysis shows that in the optimum situation, a plant with isobutane as a working fluid produces higher electricity in the day hours while no electricity is produced in the night hours. Furthermore, a plant with isobutane needs the higher evaporator pressure, mass flow rate and number of solar panels with the lower condenser pressure, storage tank capacity and regenerator effectiveness compared with R245fa and R123. Finally the sensitivity analysis on simulation time step is performed and results are reported. (C) 2015 Elsevier Ltd. All rights reserved.