It's 19% of worldwide electricity generation. http://ga.water.usgs.gov/edu/wuhy.html http://ga.water.usgs.gov/edu/wuhy.html Furthermore, hydropower may be thr

It's 19% of worldwide electricity generation. http://ga.water.usgs.gov/edu/wuhy.html http://ga.water.usgs.gov/edu/wuhy.html Furthermore, hydropower may be throttled up and down, such that the combination of hydro + wind and solar can hit penetrations near 50% before more energy storage is needed. Also, wind power is less expensive on a kwhr delivered basis than coal. http://www.stanford.edu/group/efmh/jacobson/Ia.html http://www.stanford.edu/group/efmh/jacobson/Ia.html