A growing number of US cities and states have proposed or even passed legislation that would require producing all electricity from renewable
energy sources like solar and wind within a few decades. That might sound like a great idea. But a growing body of evidence shows it's not. From a report: It increasingly appears that insisting on 100 percent renewable sources -- and disdaining others that don't produce greenhouse gases, such as nuclear power and fossil-fuel plants with carbon-capture technology -- is wastefully expensive and needlessly difficult. In the latest piece of evidence, a study published in Energy & Environmental Science determined that solar and wind energy alone could reliably meet about 80 percent of recent US annual electricity demand, but massive investments in energy storage and transmission would be needed to avoid major blackouts. Pushing to meet 100 percent of demand with these resources would require building a huge number of additional wind and solar farms -- or expanding electricity storage to an extent that would be prohibitively expensive at current prices. Or some of both.