The perspectives of the depletion of fossil energy resources, together with the consequences of climate change, have provoked the development of numerous national and pluri-national energy policies. However, there have been few overall studies on the evolution of these resources. This paper uses a dynamic model to study the exhaustion patterns of world fossil and nuclear fuels and their possible replacement by renewable energy sources. The results show that peak oil will be the first restriction and it will not be easily overcome. Electric vehicles can produce some interesting savings, but they are insufficient to avoid the decline in oil. Biofuels are even more limited, due to the enormous extensions of fertile land they require and their low productivity. This shows that overcoming the decline in oil will need much more ambitious policies than the mere substitution of technology. If the “oil–economy” relationship does not change substantially, world economic growth may be seriously limited or even negative. In contrast, the production of electrical energy is not such a worrying problem in the short and middle-term.