This paper presents sizing, energy management strategy, and cost analysis for a configuration consisting of solar photovoltaic (PV) panels, fuel cell (FC) storage system, and reverse osmosis (RO) desalination technology for combined power and fresh water production. In this system, PV is the main power supply source; fuel cell is a storage system accompanied by Hydrogen production and storage devices; and for fresh water production, RO technology is considered as desalination unit. Energy production strategy, developed on the basis of solar irradiance, hourly electricity consumption, and daily fresh water demand to minimize the capacity of components. To this goal, a flowchart diagram is designed, and sizing method is modeled using MATLAB software based on this flowchart. Finally, economic analysis for co-production of fresh water and electricity is discussed, and results of sensitivity analysis for variations of net present value (NPV) cost in terms of different fuel cell storage system prices and different interest rates are presented. Results show that described energy management strategy causes the configuration to follow hourly electrical demand and daily fresh water requirement precisely, so that the total surplus energy production during a day is very little and negligible. Moreover, calculations show that the largest part of costs is due to the energy storage system. So, while the solar PV is the main energy source and solar irradiance in Khark Island more than Astara, the overall configuration cost is greater in Khark Island just because of greater energy storage system costs, nevertheless, using such energy storage systems is necessary due to intermittent inherent of solar energy.