This paper presents a probabilistic approach based on the convolution technique to assess the long-term performance of a hybrid solar-wind power system (HSWPS) for both stand-alone and grid-linked applications. To estimate energy performance of HSWPS the reliability analysis is performed by the use of the energy index of reliability (EIR) directly related to energy expected not supplied (EENS). Analytical expressions are developed to obtain the power generated. The hybrid system and the load models employed enable the study period to range from one year to one particular hour-of-day, thus allowing the inclusion of the time-value of energy as appropriate in economic assessments. A numerical example application is included to illustrate the validity of the developed probabilistic model: the results are compared to those resulting from time domain simulations. (C) 2005 Elsevier Ltd. All rights reserved.