Energy sources of various kinds heat and power human development, but also put at risk the quality and longer-term viability of the biosphere as a result of unwanted, ‘second order’ effects. These side effects give rise to potential environmental hazards on a local, regional and global scale. Consequently balancing economic and social development with environmental protection is at the heart of the notion of sustainable development as set out in the London Communiqué; the 1997 declaration by 18 chemical engineering societies from around the world aimed at harnessing their skills to improve the quality of life. In this context, the principles and practice of sustainability are examined as they apply to the energy sector. Conflicts between the moves towards energy market liberalization and the needs of sustainable development are outlined in the light of recent experience in the United Kingdom. The likely options for a sustainable energy strategy are described, as well as some of the challenges that such approaches would pose for the engineering profession.