This work has two main objectives. The first objective is to carry out a statistical comparison of specific models for estimating monthly mean daily and hourly global and diffuse irradiations on a horizontal surface from the monthly average per day of the main meteorological data and to recommend the most accurate models to be used for estimating solar radiation in sites belonging to the Algerian climate areas represented by each of the three sites presented in this work. The second objective is to propose a Simulink program where the methodology allows for reconstituting daily and hourly monthly mean horizontal solar radiation data. From the 10 global radiation models proposed in several journal papers, Rietveld's, Garg et al.'s and McCulloch's relations are retained, respectively, for estimating the monthly mean daily global ratio for Adrar, Bouzareah and Ghardaia sites and Page and from the nine retained diffuse relations, Page's, Liu et al.'s and Erbs et al.'s relations are used, respectively. for the same sites for calculating the monthly averages per day of diffuse irradiation. On the other hand, the models of Jain and Liu et al. are, respectively, recommended for the reconstitution of the monthly averages per hour of the global and diffuse irradiations. However, the obtained results are used to develop a Simulink program which can be used in the estimation of long-term performance of flat plate solar radiation systems. (C) 2009 Elsevier Ltd. All rights reserved.