This paper presents the development of a numerical model of a hybrid cooler for transient simulation purposes as a component of a thermal energy system. The model uses a modular definition of the control volume, and is suitable for modelling any staggered coil geometry. The set of parameters required for modelling the hybrid cooler is typical of the so-called design models. A rigorous analysis of sensible and latent heat fluxes due to spray water evaporation is included. Further, the model can be exploited for the development of user-defined control strategies of fans and water spray systems. The model is validated using monitored data from a pilot system installation in which a commercial hybrid cooler is operated under typical summer south European working conditions. (C) 2016 Elsevier Ltd. All rights reserved.