According to the report, clean energy investments grew to a record $263 billion globally in 2011, a 6.5 percent increase over the previous year. The report says the U.S. attracted $48 billion in clean energy investment last year, a 42% increase over 2010. China wasn't far behind with $45.5 billion in clean energy investment, followed by Germany with $30.6 billion.

Among the G-20 nations, the world's leading economies, the U.S. continued as the top destination for venture capital and private equity investments, according the report.

Where did the money go?

For the second year, solar was the leading technology for clean energy investment globally, and the U.S. was the leading destination for solar investments. China's clean energy investments, meanwhile, spurred deployment of 20 GW of wind power, the most of any nation.

The report - Who's Winning the Clean Energy Race? – cautions that the U.S. may have trouble retaining its lead due to now-expired Treasury grants and DOE loan guarantees and the pending expiration of production tax credits at the end of 2012.

"In 2011, the global clean energy sector grew again, the U.S. reclaimed its lead as the top destination for private investment, and consumers reaped the rewards of significantly reduced prices for clean energy technologies, such as solar panels, which are now nearly 50 percent cheaper than a year ago," said Phyllis Cuttino, director of Pew's Clean Energy Program. "And yet, the yo-yo effect of U.S. clean energy policy hurts the ability of the United States to consistently compete and turn U.S.-led innovation into manufacturing, deployment, and export opportunities. Creative, stable, and transparent policies remain a critical signal to private investors."

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IDC - Perspective: Solar Energy Strategies Quarterly Update