Congress has repeatedly failed to extend the tax credits for renewable energy, which expire at the end of this year. The gridlock is discouraging investment in renewables and jeopardizing major solar and wind projects throughout the country.

After years of optimistic predictions and false starts, it looks like solar's moment is here at last. Analysts say a pattern of rapid growth, technological breakthroughs, and falling production costs has put solar power on the brink of becoming the world's dominant electricity source.