Wind power—with capital costs far lower than solar power and output comparable to fossil fuel—is emerging as the most competitive option for renewable electricity. The sheer amount of solar energy that reaches the United States each year, roughly 3,900 times our needs, makes it a fantastic choice, in theory. But developing solar technology has proven difficult. Hydrogen is clean and abundant in the natural world. Like electricity, however, it must be extracted using another source of energy, such as coal, nuclear power, or wind. Using biomass—fuel derived from plant and animal matter—to produce electricity causes no net carbon emissions, but, again, there are back-end carbon costs associated with producing the fuel. The source for all of this information is the Pew Center on Global Climate Change.