Solar on just 0.5% of landmass could produce 100% of our electricity needs.

"According to America's Department of Energy, solar panels could, if placed on about 0.5% of the country's mainland landmass, provide for all of its current electricity needs. Yet since they were first invented more than five decades ago, photovoltaic solar have generated much publicity but little energy. In 2006 photovoltaic systems produced 0.04% of the world's electricity, according to the International Energy Agency.

Decades of research have improved the efficiency of silicon-based solar cells from 6% to an average of 15% today, whereas improvements in manufacturing have reduced the price of modules from about $200 per watt in the 1950s to $2.70 in 2004. Within three to eight years, many in the industry expect the price of solar power to be cost-competitive with electricity from the grid." From The Economist.