Guided by numbers, not adjectives, MacKay, a Cambridge University physicist, provides a critical look at the diverse possibilities for introducing renewable energy (including nuclear energy). Merely describing the possibilities for wind or tidal energy as "huge," for example, is not helpful if the objective is to actually reduce climate change or eliminate the need to import oil and coal. Irritated by the "flood of crazy innumerate codswallop" to which the public is subjected, the author sketches the actual possibilities for harnessing renewable energy with today's and tomorrow's technologies. His calculations are for the United Kingdom, but the basic physics applies to all countries. He predicts that the United Kingdom will fall far short of the EU's objective of supplying 20 percent of all its energy with renewable sources by 2020. That would require massive investments and would use massive amounts of land and coastline (the book specifies how much of each), even with extensive energy-conservation efforts. This is a useful, down-to-earth handbook on what is possible, what is difficult, and what is impossible when it comes to phasing out the use of fossil fuels.