Things are moving fast in renewable energy. Really fast. Consider that in 2008 wind farms supplied just 1.5% of all electricity in the United States. But by 2019 wind power is expected to contribute 6.9% of American electricity and overtake hydropower as the top renewable energy source.The rise of wind power wouldn't have been possible without two companies in particular, which combine to own 20.7 gigawatts of wind capacity, or about 24% of the country's total.