Previous efforts on modeling energy, the environment, and climate change perspectives are critically examined, and the structure of energy and an environment system model is described. Focus is on sustainable development using Bangladesh as an illustrative example. The model projects energy supply and demand and its contribution to global warming. Simulated results show that the demand for electric energy is increasing, and there is a shortage of electric power. Electricity generation capacity can increase by either transition to nuclear or renewable energy resources or both. However, generation capacity needs to be increased for sustainable development, with gradual transition to renewable energy resources. Mini-grids are advocated for supply of energy, information and communication for rural development and economic growth in isolated areas such as islands. Bangladesh is responsible for a small fraction of the total anthropogenic contribution of CO₂ but could be seriously affected by climatic change. Energy security aspects are also addressed. Regional economic cooperation and sustainable peaceful resolution of long-standing disputes may help the regional entities to enhance their individual and collective energy security.