Measuring the sustainability of goods and services in a systematic and objective manner has become an issue of paramount importance. Life cycle sustainability assessment (LCSA) is a holistic methodology whose aim is to integrate into a compatible format the analysis of the three pillars of sustainability, namely, economy, environment, and society. Social life cycle assessment (S-LCA) is a novel methodology still under development, used to cover the social aspects of sustainability within LCSA. The aim of this article is to provide additional discussion on the practical application of S-LCA by suggesting a new classification and characterization model that builds upon previous methodological developments. The structure of the social analysis has been adapted to maintain coherence with that of standard LCA. The application of this methodology is demonstrated using a case study—the analysis of power generation in a concentrated solar power plant in Spain. The inventory phase was completed by using the indicators proposed by the United Nations Environment Program/Society for Environmental Toxicology and Chemistry (UNEP/SETAC) Guidelines on S-LCA. The impact assessment phase was approached by developing a social performance indicator that builds on performance reference points, an activity variable, and a numeric scale with positive and negative values. The social performance indicator obtained (+0.42 over a range of –2 to +2) shows that the deployment of the solar power plant increases the social welfare of Spain, especially in the impact categories of socioeconomic sustainability and fairness of relationships, whose results were 1.38 and 0.29, respectively.