The most-used thermodynamic CSP (concentrating solar plants) in the world, provided with linear parabolic collectors cooled by oil, have been analyzed in the two configurations employed: with heat storage in two tanks filled with molten salts and without heat storage. The performances and the costs of the plants have been analyzed in the paper according to solar multiple (ranging between 1 and 3) and to storage capacity (ranging between 0 and 24 h), in terms of annual electrical energy, average annual plant efficiency, charge factor, capital cost and levelized cost of energy (LCOE). Also a method of economic optimization, based on the evaluation of the minimum value of the levelized cost of energy is presented. The minimum LCOE value, in the case of heat storage, is obtained fora solar multiple of 2.2 and a storage capacity of 16 h. In the plants without storage, minimum LCOE is achieved for SM (solar multiple) equal to 1.2. (C) 2015 Elsevier Ltd. All rights reserved.