In 1892 the Pearl Street Station ran at 2 percent efficiency—which is to say, it transformed about 2 percent of the potential energy in the coal it burned into electricity—twelve years later the Harrison Street Station had an efficiency rating of 12 percent and Fisk Street, Chicago’s first AC power plant, completed in 1903, did even better. By 1940 even average power plants were running at 20 percent efficiency. One can see why Insull found technological improvement such a promising route toward profitability.
