A simplified model for indirect cooling towers behaviour is presented. The model is devoted to building simulation tools and fulfils several criteria such as simplicity of parameterisation, accuracy, possibility to model the equipment under various operation conditions and short computation time. On the basis of Merkel's theory, the model is described by using the Effectiveness-NTU method. The model introduces only two parameters, air-side and waterside heat-transfer coefficients which can be identified from only two rating points, data easily available in manufacturers' catalogues. Thus, the model allows one to estimate energy and water consumptions under different operating conditions Such as variable wet-bulb temperatures or variable airflow rates. (C) 2003 Elsevier Ltd. All rights reserved.