The future “smart grids” will feature significantly higher numbers of various distributed generation and storage (DG&S) systems, as well as a wide-scale implementation of different demand-side management (DSM) functionalities. In existing literature, related analysis mostly concentrates on the operation, control and planning aspects of “smart grids”, while their impact on, and potential for improving system reliability performance is less researched. The work presented in this paper offers a new methodology for assessing reliability performance of power systems with fully employed DSM and DG&S functionalities, allowing to quantify in the most realistic manner standard set of indices reported annually to the Regulators. The methodology extends conventional reliability assessment procedures to include equivalent network models, actual load profiles and empirical fault probability distributions in the analysis, allowing to make a clear distinction between the short and long supply interruptions. Different DSM and DG&S scenarios are considered, in order to validate the proposed methodology and demonstrate its accuracy and applicability.