The evaporating process is very important in the system concerned with liquid foods, seawater distillation and wastewater treatment, which is to concentrate the aqueous solution by evaporating the pure water usually at a vacuum state. In general, the liquid concentration is performed through the membrane, electro-dialysis, and evaporation; the former are separation process and the latter is the phase change process. In this study, only the thermal process was treated for evaluating the specific energy consumption by changing the operating conditions of an existing MSF (multi-stage flashing) desalination plant, which is still dominant for a large scale distillation plant. This study shows the quantitative energy saving strategy in sweater distillation process and, additionally, indicates that the performance of the multi -stage evaporating system can be increased with the elevation of a TBT (top brine temperature). The calculated results were based on the operating data of the currently installed plants and suggests the alternative to improve the performance of the MSF desalination plant, which means that the energy saving can be achieved only by changing the operating conditions of the existing MSF plants. (C) 2016 Elsevier Ltd. All rights reserved.