Fuel-conversion efficiency in the U.S. electric industry has gone down over time:
The graph is titled “U.S. electric industry fuel-conversion efficiency,” and it starts in 1880 with an efficiency of 50%. It reaches a peak of nearly 65%, circa 1910, before beginning a long decline to around 30%, at which level it has been from about 1960 to the present.
How can this be? Were the reciprocating steam engines and hand-fired boilers of the early power plants somehow more efficient than modern turbines?
Not at all. The efficiency of the conversion of fuel into electricity has improved, according to the graph, by about 6:1. What has been lost, though, is the efficiency gained through the use of left-over heat. In many early power plants, waste heat was distributed (as steam or hot water) through a network of pipes permitting it be be sold to local homeowners and businesses. This practice is still used in New York City, where it dates back to Edison’s day. But the use of “district heating,” as it is known, has become much less common in the U.S. than it was in the late 1800s and early 1900s. (These systems are still heavily used in some other countries, including Denmark, the Netherlands, and Finland.)