The increased pressure on companies to address sustainability issues has resulted in the development of several voluntary corporate sustainability integration approaches. The array of existing approaches is large and overwhelming, resulting in companies not understanding what corporate sustainability really means for their businesses. Considering environmental, economic and social issues, this paper aims at assessing the performance of the Brazilian electricity power industry in terms of its sustainability performance. An analysis of Global Reporting Initiative (GRI) indicators for the energy sector lead to an assessment of its sustainability performance by applying Data Envelopment Analysis (DEA) specified with a directional distance function (DDF). Five scenarios were created: (i) Flexible weights; (ii) Triple bottom line; (iii) Social issues; (iv) Economic issues; and (v) Environmental issues. With considering (i) flexibility weights, almost all companies are efficient. We also found a significant difference when we compared (i) with the other four scenarios (ii, iii, iv and v). Taking into account the triple bottom line scenario (ii), the results indicate that companies were less efficient when compared with the flexible weights scenario (i). Taking into account the last three scenarios (iii, iv and v), only four companies were considered as providing top benchmarks in sustainability performance.