A steady-state mathematical model of a vertically stacked forward feed multi-effect distillation (MED) plant has been carried out using a number of simplifying assumptions. The model has been developed taking into consideration the same design and operational characteristics as the pilot MED plant at Plataforma Solar de Almería (PSA), in the southeast of Spain. It is a forward feed MED plant with preheaters, which uses low steam temperature coming from a parabolic-trough solar collector field as the thermal energy source. The pilot plant has a special distillate distribution for increased energy recovery which has also been taken into account in the model. This model is simple to implement and suitable for its use in optimization of water production in power and water cogeneration systems. The results of the model have been compared with the experimental data of the pilot plant showing a maximum prediction error of 9%. •A steady-state mathematical model of a MED plant has been carried out•The model takes into account the same characteristics as the pilot MED plant at PSA•The pilot plant has a special distillate distribution for increased energy recovery•The validation of the model resulted in a maximum prediction error of 9%