China has surpassed the United States as the top investor in clean energy with the rising Asian power becoming a "powerhouse" in the emerging field, a study by environmentalists said.
Nations seen as struggling in the clean energy competition include the United States, Australia and Japan, the study said.
The report said China has shown determination to be on the frontline of green technology while US investors have been put off by uncertainties amid the legislative battle on climate change.
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Chinese investment in clean energy soared by more than 50 per cent in 2009 to reach 34.6 billion dollars, far more than any other country in the Group of 20 major economies, the study led by the Pew Charitable Trusts said.
Total US investment was about half that at $US18.6 billion ($A20.5 billion), the first time in five years that the world's largest economy lost the top spot in clean energy, the study said.
"China is emerging as the world's clean energy powehrhouse," Phyllis Cuttino, global warming campaign director of the Pew Environment Group, told reporters on a conference call.
"This represents a dramatic growth when you consider that just five years ago their investment totaled $US2.5 billion ($A2.76 billion)," she said.
Of the US, Australia and Japan, Cuttino said the three nations had "less consistent, clear and long-term policies in place."
China has also overtaken the United States as the top emitter of carbon blamed for global warming and came under fire for its role in December's much-criticised UN climate summit in Copenhagen.
But the study found that China had made a strategic decision to invest in wind and solar technologies as it copes with sharply rising demand for energy - and had set some of the world's most ambitious targets on renewable energy.
The study also found strong investment by Britain, which ranked third with $US11.2 billion ($A12.35 billion) for clean energy; Spain, which came in first in green investment when taken as percentage of gross domestic product, and Germany.
US President Barack Obama, Australian Prime Minister Kevin Rudd and Japanese Prime Minister Yukio Hatoyama have all championed climate action but none of the countries have set in motion nationwide plans to curb emissions.
But the study noted Australia had potential in wind energy and said Japan was "one of the G-20's most promising growth markets" if the resource-poor nation carries out plans to ramp up solar and wind power.
The study found that even though the US dominates technological innovation, its investment in clean energy tumbled 42 per cent last year from 2008 levels.
The researchers partly blamed the global economic slowdown but also said there was a lack of direction. Climate legislation has been stalled in the Senate, although Obama allies have vowed to push it ahead now that Congress has completed the top priority of expanding health care.
Obama and his congressional allies argue that curbing emissions will open up a new green economy, helping fuel the economic recovery.
