In this paper a model is presented for the technical and economic sizing of the various components that make up medium sized wind-powered pumped hydrostorage systems. A further aim of this model is the optimisation of the operation of such systems, thereby making full use of the synergy of the unit as a whole. A general model is described for use as an analytical tool in implementing such systems in topographically suitable sites with sufficient wind resources. The general model developed allows for six strategies for the system operating configuration. Each strategy is based on the hypothesis that there is a centralised operator to control all the system components, except for the load systems. The characteristics and unit energy cost of each technically feasible combination of components are determined by applying the model. This enables the selection of the most viable composition for the system from an economic point of view given certain technical restrictions. (c) 2004 Elsevier Ltd. All rights reserved.