After decades on the fringe, solar power is closing in on America's mainstream as surging fossil fuel prices and mounting concern over climate change spur states, businesses and homeowners to embrace alternative energy.
Solar panels are still too expensive in most regions to compete with cheaper, less environmentallyfriendly fuels like coal without generous subsidies.
But not for long, industry analysts and scientists say.
The tipping point at which the world's cleanest, most renewable resource is cost-competitive with other sources of energy could happen within two to five years in some regions and other countries if the price of fossil fuels continues to rise at its current pace, they say.
"In the long run - as in two to three years - you should see competitiveness, especially with the grid in a number of regions in the world," says Vishal Shah, an analyst who tracks the industry at United States investment bank Lehman Bros.
Tom Werner, chief executive of SunPower, the largest US solar company by sales, forecasts "grid parity" for solar power in about five years or possibly as soon as 2010.
In the US, much depends on November's elections. A Democratic win of the White House, and possibly greater Democratic control of Congress, could spur aggressive measures to limit climate-warming emissions and make solar and other cleaner energy sources more competitive.
Although solar power is easily installed, building solar panels is expensive because of tight supplies of silicon, their costliest element.
Most industry analysts expect a constraint on silicon supplies to end within two years. But rival technologies are emerging, such as thin-film panels that require almost no silicon, raising the possibility of a costly battle in the solar-power industry.
Under laws in 25 US states, solar and other clean energy sources must constitute up to 30 per cent of a utility's energy portfolio in five to 15 years. Just 10 states had such requirements in 2003.
The US - the world's fourth-largest solar-power market after Germany, Japan and Spain - saw nearly 150 megawatts of solar capacity come online last year for a total of 750 megawatts, says the Solar Energy Industries Association, a US trade group.
If subsidies continue, the US could generate as much power from solar panels as 2 1/2 nuclear reactors in four years - or about 2.55 gigawatts, says the European Photovoltaic Industry Association. *
