More fresh electricity capacity was added to the electricity grids of both the United States and Europe last year from wind turbines, solar panels and other renewable sources than from conventional power plants run on fossil fuels and nuclear energy.
It was the second year in a row that renewable energy beat its conventional competitors.
The findings are being released Thursday in reports jointly issued by the United Nations Environment Program and Paris-based Renewable Energy Policy Network, which said green energy has "reached a clear tipping point" in becoming the dominant type of new electricity supply.
China had the largest addition of renewable power capacity, and the Asian economic powerhouse surpassed the United States as the country with the largest investment in clean energy.
China now produces about 40 per cent of the world's solar electricity collectors, 25 per cent of its wind turbines, and three-quarters of its solar water heaters.
The organizations predicted that capacity additions of renewable sources of electricity will exceed new conventional sources either this year, or in 2011, on a worldwide basis.
The figures and the projections of continued growth in green power are leading some analysts to suggest the electricity market, long dominated by high-polluting coal, is starting a long-term switch to cleaner generation sources.
Electricity supply is "in transition from a world that was powered by fossil fuels to one that's going to be powered by renewable sources of energy," said Lester Brown, president of Earth Policy Institute, a Washington-based environmental think tank. "I think the lines have crossed permanently on this."
The BP oil well blowout in the Gulf of Mexico will likely drive more investment in the green sector, he said. "This debacle in the Gulf is only going to reinforce it."
Spending on green energy remained buoyant in 2009, despite the global recession, with investors pouring $162-billion (U.S.) into windmills, solar panels, biomass plants and other clean electricity sources. The amount was down 7 per cent from the record investment of 2008, but nearly quadruple the level 2004.
Share prices in the green-power sector rose about 40 per cent in 2009, but underperformed stock markets by about 10 per cent in the first four months of this year because low electricity and natural gas prices cut the profitability of energy projects.
Governments have promoted renewable energy in their stimulus programs, earmarking about $188-billion for the sector. By the end of 2009, only 9 per cent of the money had been spent, contributing to the optimism for new capacity installations this year and in 2011.
Wind was the dominant clean energy sector in 2009, accounting for $59-billion, or 45 per cent of new spending on sustainable electricity. Solar photovoltaic investments were a record $40-billion, with Germany the top investor, accounting for about half the market.
While traditional electricity sources, such as coal plants, face investor uncertainty over possible carbon pricing and cap-and-trade schemes, the organizations said "a significant milestone" was reached earlier this year, when the number of countries enacting measures to promote renewable energy rose to more than 100, up from only 55 in early 2005.
Follow us on Twitter: