America’s shale gas boom: 'Over the last five years, as the U.S. has improved horizontal drilling techniques aimed at extracting natural gas and oil from tight shale formations, the price of natural gas has gone from about $13 per 1 million BTUs in 2008 to a low of less than $2 last April. At the same time, natural gas in Europe has stayed above $10. In the U.S., all that cheap natural gas has displaced coal as a source of electricity. The U.S. generated 30 percent of its electricity from natural gas in 2012, up from less than 20 percent in 2005. The price of coal fell, too, but it couldn’t keep pace with the steep declines in natural gas. As a result, coal’s share of electricity generation fell to about 40 percent, down from 57 percent in the mid-1980s'