That’s not quite right, I think, because you can run a coal plant irrespective of the weather so a megawatt-to-megawatt comparison is kind of misleading. That said, the point remains that renewable energy is not some outlandishly expensive hypothetical alternative. If the much-poorer United States of 1957 could afford coal power, the much-richer United States of 2007 can afford solar (and wind, etc.) power. And if the rich world decisively commits itself to renewable electricity, the number of firms trying to find cost-effective ways to deliver this sort of electricity will skyrocket, developing the sort of methods and technologies that can be viable on a mass basis in India and China.