15% is a lot, actually it could be anywhere from 7-15%. Even if lowest power estimate was reached due to this which is 20000MW, 3 States like Karnataka can be powered without need to use any other electricity and no power cuts. This should give you an idea about the magnitude. If we hit 40000MW which some folks are now predicting, it will be enough to power 1/4th of India on current power usages. Friend don't get confused too much in percentage terms. We are talking big numbers here.