This study aims to make the economic assessment of five Desalination Systems by Reverse Osmosis (RO) that are used to generate fresh water for human consumption in rural communities in the Ceará State. The data was gathered from primary source by questionnaire applied to governmental organizations. The method used was the analysis of investment taking into account shadow prices. We concluded that due to the inexistence of any good practices for the desalination management some equipment resulted in negative financing return when considering the effective consumption, particularly those of 400 and 600 liter/hour. In addition, they generated inefficiency regarding to technical support, turning impossible better improvement of the system performance, thus leading to insecure water supplies and unsatisfied demand. Given the limitations imposed by the managers, low production and system failures, which resulted in constant systems’ interruption, the effective demand of fresh water was restricted to the half of the working capacity of the system.