This paper presents a novel approach for daily Volt/Var control in distribution systems using Distributed Generation (DG) units. The impact of DG units on Volt/Var control is significant in a distribution network with radial configuration and small X/R ratio. in this paper, a price-based approach is adopted to determine the optimum active and reactive power dispatch for the DG units, the reactive power contribution of the capacitor banks, and the tap settings of the transformers in a day in advance. A fuzzy adaptive particle swarm optimization (FAPSO) method is used to solve the daily Volt/Var control which is a non-linear mixed-integer problem. A mathematical expression of the proposed method and its effectiveness using simulation results are provided. (C) 2010 Elsevier Ltd. All rights reserved.