By the mid-1960s it had become clear to utility men that a plant run at just over 30 percent efficiency was both the most reliable and the most cost-effective way to make electricity. The truth of this has not changed in the fifty years since. In 2012, the best fossil fuel power plants in America ran at 42.5 percent efficiency—but this number is only for a few natural gas combustion (no-steam) turbines. The newest steam plants operating in the United States between 2007 and 2012, whether fueled by coal or plutonium or petroleum, came in right around 34 percent efficiency.
