LAS VEGAS -- A sharp, long-term fall in the price of solar cells has led The Economist magazine and others to declare that in some parts of the U.S. - sunny areas with high electricity prices - solar power is now cheap enough to compete without government subsidies.

Rory McIlmoil, program manager for the energy program at environmental consulting firm Downstream Strategies, says that applies to places such as California and the Southwest, but not the East Coast - yet.

"In those areas, solar is competing with other sources of energy that have higher electricity prices than we experience here, which makes it a lot more likely that solar can compete."

One central criticism of renewable-energy sources such as solar power is that they are too expensive. According to McIlmoil, that is rapidly changing, as solar's explosive growth shows. The price of building a solar power plant is nearing the point where it would be competitive with a new coal plant of a similar size, he says. Both cost more than a natural-gas plant, but he points out that solar has the advantage of free fuel.

"Natural gas peaker plants have other costs associated with their operation that solar power does not: High fuel and - depending on the size - high maintenance costs for your traditional power plants versus solar power plants."

Solar also is limited by the inconsistent nature of sunshine, although McIlmoil says power storage and flexible use of the grid are easing some of those issues. Thanks to cheap solar cells, he says, 2010 saw what was then a record level of solar power installed.

"And just one year later, twice that much was installed. Roughly 80 percent of the solar power that currently exists in the United States was installed just over the last three years."

The solar industry still depends on significant federal subsidies, although overall, McIlmiol says, the much larger fossil-fuels industries actually receive more in tax breaks.

The Economist article is online at www.economist.com.