Principal environmental challenges and opportunities A sustainable energy model must satisfy various political objectives, such as the economic objective, which can be summarized as the need for stable, safe, and competitive supplies of energy (or safety and a guaranteed resource); the social objective, which is refl ected in access to this essential service for all persons under economically feasible conditions (or competitiveness and the universality of service); and the environmental objective, which consists of fewer emissions and greater effi ciency in the production and use of energy, as well as compliance with environmental regulations.