This paper presents the application of a business case model for the implementation decisions to be done by utility companies. The goal is to modernize the grid and their business, leveraging the potential of the smart grid (SG) for the benefit of the company and the customers (economically and socially), as well as the environment. The company selected for this research is a spanish distribution and retail utility Empresa de Alumbrado Electrico de Ceuta (EAECSA). Being an isolated power system with limited extension, it proves useful as an example for larger systems and to test the proposed model. From the characteristics of the grid and the regulatory and strategy mandates, the best alternatives are calculated using a model based on the relation between each of the SG functions parameters and a prioritization factor, detailed in the paper. The assessment of actually available technologies and functions is first presented with a strategic and business approach, as a way of filtering appropriate technologies for implementation. The second step is to assess the case for each technology and function, in order to select the most impactful solutions in cost to benefit ratio. The resulting roadmap is a guide for technology implementation in the best economic, environmental and social way, proving the model a useful tool for an integrated approach to the introduction of SG technologies.