In 2019 -- or possibly even this year -- wind power will become America's top source of renewable energy power generation, and provide around 7% of the country's total electricity. The magnitude of that cannot be understated: It will be the first time since the late 1800s that hydroelectric power won't be the nation's most productive renewable energy source.Many stakeholders and technologies have played a role in this changing of the guard, but two companies in particular made incredible contributions: NextEra Energy (NYSE: NEE) and Xcel Energy (NASDAQ: XEL).