The integration of Pressure Retarded Osmosis (PRO) with Seawater Reverse Osmosis is studied here in terms of energy recovery and changes of effluents. For this, two alternative integration designs are evaluated: one-stage PRO and a proposed two-stage PRO. For both designs the analysis is carried out without using external impaired water flows. The results show better performance of the proposed two-stage PRO. The study of operating conditions revealed that the increase of the feed concentration and the feed flow improves the performance of PRO. Lastly, for the proposed designs, the increase of the second stage recovery worsens the energy balance.