As a result of the dissemination of the sustainability concept, social disclosures have become an important area of non-financial reporting, and the energy sector is no exception. The purpose of our article is a multi-faceted evaluation of sustainability reports published by companies operating in the Polish energy sector, from the perspective of social disclosures. The study involved the Polish listed companies that made up the WIG-Energia index. The time scope of the study covers the 2017−2021 period. In total, 54 non-financial reports were analyzed. In the first place, a comparative analysis was carried out to assess the social disclosures made by the WIG-Energia companies against the background of the biggest and the most liquid (blue chip) WIG20 companies. All the applied tools: ESG rating, NFR_S index, and multidimensional data visualization, have confirmed that the energy companies year by year have been presenting larger and larger extents of social disclosures. At the same time, it was observed that the companies appearing for the first time in the WIG-Energia index showed a very small extent of disclosures, whereas the companies which figured in the index throughout the studied period presented a relatively large extent of disclosures, due to their experience in preparing sustainability reports. Next, using the Pearson correlation coefficient (r), we examined the relationship between the energy companies’ market values and the extent of their social disclosures. The results of the statistical analyses have validated the strong and very strong correlation between capitalization and extent of disclosures. It is therefore possible to state that companies with higher market values are characterized by larger extents of social disclosures.