Subsidies are needed because solar is still more expensive than conventional power sources like coal, but costs are dropping by around 5 percent a year and "grid parity", without subsidies, is already a reality in parts of California.
Very sunny countries could reach that breakeven in five years or so, and even cloudy Britain by 2020.
"At that point you can expect pretty much unbounded growth," General Electric Co's Chief Engineer Jim Lyons told the Jefferies conference in London on Thursday, referring to price parity in sunny parts of the United States by around 2015.
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