On this topic, Kurzweil is quite bold: He thinks that solar power is growing exponentially, so it will supply 100% of the WORLD’S (not just America’s) ENERGY (not just ELECTRICITY) within 15 years. Additionally, his predictions are unambiguous in their wording and deadlines, rendering them highly amenable to objective evaluation. For better or worse, he won’t be able to talk his way out of this......Note that his deadline for 100% solar power has fluctuated over the last 13 years from 2025 to 2033, and I suspect it will continue to do so (Kurzweil will probably do something like bump it up by ~1 year every 2 years). His statements about the number of exponential “doublings” left until solar power supplies 100% of humanity’s energy also barely withstands arithmetic scrutiny (If solar power’s electricity output is doubling every two years, then why did he say it was 8 doublings away from 100% in 2011, but then say it was still 8 doublings away in 2013? Since two years had passed between the predictions, shouldn’t it have been down to 7 doublings in 2013?).