we are not exactly sure for how much longer fossil fuels are going to last. Some say 50 years some say 100 years. One of the reasons for not knowing for sure is that oil extracting companies dont tell us exactly how much oil they have left in their drilling areas. But the certainty is that fossil fuels will run out and that while we keep using them they pollute our planet and also become more and more expensive. In some countries already, it is cheaper to produce electricity from the sun rather than using oil.