I learned about the Jevons paradox at PyCon Portugal from Pablo Galindo Salgado apropos something I can't remember. Initially observed in the 19th century, when the steam engine became much more efficient, folks expected coal usage to decrease – after all, the engine was now much more efficient. Instead, overall coal usage increased because the better efficiency lead to an increased adoption of the steam engine. This increased adoption of the steam engine outweighed the increased efficiency, meaning the net effect was that more coal was being consumed.