This dissertation presents, through a case study, the development of a multicriterion decision model to create a Quality Index to evaluate the service provided by a distribution electricity utility. The study used an iterative process following the approach proposed by MACBETH software. The thesis shows the different components of this social-technical process adopted. MACBETH requires solely qualitative judgments about the attractiveness differences among the elements in order to generate the weights and the marks for each criterion. This type of judgment procedure motivates the discussion and the learning process among the members of the working group, which results in a real contribution to development of a group value system. The multicriterion model developed is general enough to allow its implementation to others distribution electricity utilities. This proposed index can be easily adapted and acts as a comparison measure of the quality of the services provided by utilities. Therefore, the present thesis also brings about a contribution to the regulator agent which is searching for quality index that is robust enough to be implemented in any distributing utility.