Significant improvement in reverse osmosis (RO) membrane permeability makes the emergence of thermodynamic restriction in desalting process. Due to the filtration flux, both the accumulation of rejected solute and the subsequent concentration polarization layer contribute to the transmembrane osmotic pressure difference that needs to be overcome by the applied pressure. A theoretically derived formula predicting the permeate flux accounting for pressure drop, effect of applied pressure on solute rejection and concentration polarization is presented, and the obtained average rejection is used to calculate the operating energy consumption of RO process more accurately. On the basis of theoretical considerations, at the limit imposed by thermodynamic restriction, an energy consuming analysis model of RO process was developed to study the effects of RO operating parameters (e.g., recovery rate), energy recovery devices (ERDs) performance variables (efficiency and leakage ratio), and pump efficiencies on the specific energy consumption (SEC).