Even though black gold has been in steep decline, it's still the most-used electricity generation source in 18 US states, according to government statistics published this week. Not even natural gas, a rapidly growing and cleaner burning fuel, leads in that many states. The numbers underscore how large pockets of America continue to rely heavily on coal for power and jobs. "It's hard to unseat a former champion. It doesn't change overnight," said Matt Hoza, manager of energy analysis at consulting firm BTU Analytics.