The IAEA offers its Member States a comprehensive programme of technical assistance and cooperation, which covers many diverse areas related to peaceful uses of nuclear energy. In the area of energy planning, the IAEA provides assistance to Member States to strengthen national capabilities for elaborating sustainable patterns of energy supply and use. This publication is a successful example of implementing an energy planning project in Mexico. It can serve as a guideline for designing and implementing similar projects in other countries, addressing the economic, social and environmental issues of energy sector development.