The performance improvement obtained from the use of trackers in a PV system cannot be separated from the higher requirement of land due to the mutual shadows between generators. Thus, the optimal choice of distances between trackers is a compromise between productivity and land use to minimize the cost of the energy produced by the PV system during its lifetime. This paper develops a method for the estimation and optimization of the cost of energy function. It is built upon a set of equations to model the mutual shadows geometry and a procedure for the optimal choice of the wire cross-section. Several examples illustrate the use of the method with a particular PV system under different conditions of land and equipment costs. This method is implemented using free software available as supplementary material. (C) 2011 Elsevier Ltd. All rights reserved.