For the past century and a half, the developed world has relied on petroleum and its by-products for a large proportion of our energy needs. The reason oil has been so dominant is easy to figure: it's remarkably energy dense and at the same time it's far cheaper than any alternative. Recently Ed Kinderman and Hewitt Crane at SRI International, in Menlo Park, California decided to come up with a new way of measuring alternatives to petroleum. They determined that the world currently consumes about one cubic mile of oil (CMO) annually. To get an equivalent amount of energy to that CMO, we would have to produce 104 coal fired power plants, every year., FOR 50 YEARS! Similarly, we would need 52 new nuclear power plants or 4 Three Gorges dams. Every year! FOR 50 YEARS!. That's just to get the same amount of energy we get from that one cubic mile of oil we consume every year.
[Source IEEE Spectrum via Wired