a whole year or argue that wind power could theoretically supply all the world's electricity. The other side of the cacophony responds with a litany of its own: Renewables are pathetic, intermittent and expensive. They are not good but bad for the environment. And ugly. Neither is very illuminating. To have constructive conversations about the world's energy options, one needs to take a calm look at the numbers. How much energy does our chosen lifestyle use? How much land area do we have? And how much could we produce, from each source, and at what cost? The average energy consumption on earth is 56 kilowatt-hours per day per person. You can visualize this personal energy consumption in terms of light bulbs: 56 kilowatt-hours per day is the energy consumption of 56 ordinary 40-watt bulbs left switched on all the time. The world's population density is roughly 50 people per square kilometer, or 0.4 square mile. Countries, of course, vary significantly around the world average. When considering the potential of renewables to power a country, it's critically important to know that country's power consumption per unit area. The graphic accompanying this article plots where a variety of countries fall on the scale. The countries with the highest power consumption per area are those, like Bahrain, that have high population density and high per-capita consumption. Bahrain consumes more than 10 watts per square meter, or 11 square feet. The lowest are countries like Botswana and Sudan, at less than 0.01 watt per