In the context of global concerns about climate change that stem from the alarming and unprecedented growth of greenhouse gas (GHG) emissions, this study discusses the use of energy by large consumers of electricity in Brazil in the perspective of sustainable development, energy resources, and regulatory policies. It evaluates the commitment to emissions restrictions among the major customers of an electricity utility company that serves 4.1 million consumers (68% of the population and 66% of the gross internal product for the second-highest economically developed Brazilian state). The evaluation is based on proposed metrics and indicators. By considering the Brazilian commitment to a policy of sustainable development, this study reviews the primary international agreements and recommendations that have been developed to mitigate and adapt to climate change and sustainability. A survey was developed for participating organizations classified by economic sector to assess their awareness to 18 issues that reflect international guidelines on emission constraints. Based on total energy consumption, the survey discusses the worrying level of GHG emissions (tCO2eq) that is associated with the generation of electricity by customers of the largest utility company. In spite of 90% of the organizations having considered sustainability as a business opportunity and a competitive differential that enables niche markets, the results of this study demonstrated low commitment to the desired emissions restrictions.