Editing Net energy gain (section)

===Examples===
[[File:Net energy cliff.gif|thumbnail|Net energy cliff with degrading EROI]]

During the 1920s, {{convert|50|oilbbl|m3}} of [[crude oil]] were extracted for every barrel of crude used in the extraction and refining process. Today only {{convert|5|oilbbl|m3}} are harvested for every barrel used. When the net energy gain of an energy source reaches zero, then the source is no longer contributing energy to an economy.{{Citation needed|date=December 2017}}