Linear Fresnel power plants are currently one of the most promising concentrating solar power plants. However there are only a few commercial projects. These power plants have a lower efficiency than parabolic trough collector plants and are still expensive. To increase the efficiency of these plants, the utilization of water/steam in the receivers (direct steam generation, DSG) and thermal storage (TES) have been considered. As case study, a 50 MWe solar-only linear Fresnel power plant located in Seville, Spain is considered. The effects of the solar field size and the thermal storage size on the annual production of the plant are analyzed: Nine different solar field sizes and up to eight thermal storage sizes have been compared. An economic optimization is presented in order to determine which plant has lowest Levelized Cost of Electricity (LCOE). It has been found that for the power plants with no-storage the optimum solar multiple (SM) is 1.7, whereas for the cases with thermal storage, the optimum configuration is a larger solar field (SM = 2), with a thermal storage of 2 h.