Although defining sustainable development is not trivial, it may be thought of as economic development that offers quality of life for all within the carrying capacity of nature, stressing how human activities are constrained by economic, social and environmental limits. It may also be described as total sustain ability, stipulated for the satisfaction of human needs, through socially accepted technological systems and appropriate policies and political instruments. Energy is an important concern in sustainable development, leading to significant environmental pressures at the global, national, regional and local levels. Electricity production in many countries is based on a variety of energy sources (including solid mineral fuels, oil, gas, nuclear power and RES) and is an important contributor to economic development. The energy industry is the basic factor for both the development of the economy and the improvement of quality of life, in combination with environmental protection. RES offer great potential for sustainability and are emerging as technically feasible, economically viable and socially acceptable alternatives. Power generation may become greener as a result of a reduction in carbondioxide emissions, which may be achieved by a shrinking of the share of fossil fuels accompanied by an increase in renewable energy generation in the final mixture. RES such as solar, wind and biomass play a vital role in meeting the growing energy demands of developing countries. The most important key indicators of sustain ability that can be assessed are the price of electricity generation, the energy pay-back time, greenhouse gas emissions, the availability and limitations of each technology, the efficiency of energy transformation, the land use requirements and the social impacts. RES ensure a balance between economic, technical and environmental systems.