Renewables surpass coal in power mix

For the clearest sign yet that renewable energy has gone mainstream, consider this: Clean energy resources supplied more of America's electricity than coal for the first time ever in April.

Hydropower dams, solar panels and wind turbines generated almost 68.5 million megawatt-hours of power in April, eclipsing the 60 million that coal produced that month, Energy Information Administration data released late Tuesday show.

That's the most clean power the United States has ever made - and the least coal it has burned for power in years.

The shift is a testament to the rapid development of solar and wind farms across the country.

The two forms of power have become so cheap to build that BloombergNEF, a research organization, is projecting that half the world's power may come from renewable energy by 2050.

The onslaught of clean power is coming largely at the expense of coal, which only a decade ago supplied more electricity in the United States than anything else.

One of the main reasons coal-fired power plants produced so little in April was because some were down for routine, springtime maintenance. Coal is forecast to return to its perch as the second-biggest source of electricity - after natural gas - as those units return to service and demand peaks this summer.

Michael Bloomberg, founder and majority stakeholder of Bloomberg LP, the parent company of Bloomberg News, has committed $500 million to launch Beyond Carbon, a campaign aimed at closing the remaining coal-powered plants in the United States by 2030 and slowing the construction of new gas plants.