Editing Net energy gain (section)

== ISO 13602==
[[International Organization for Standardization|ISO]] 13602-1 provides methods to analyse, characterize and compare technical energy systems (TES) with all their inputs, outputs and risk factors. It contains rules and guidelines for the methodology for such analyses.<ref name="Grobe">{{cite web|url=http://www.internationalenergyworkshop.org/pappdf/Grob.pdf|archive-url=https://web.archive.org/web/20081217082444/http://www.internationalenergyworkshop.org/pappdf/Grob.pdf|url-status=dead|archive-date=2008-12-17|title=Technical Energy Systems - Methods for Analysis|date=2002-11-01|publisher=[[International Organization for Standardization]]|access-date=2008-11-24}}</ref>

ISO 13602-1 describes a means of to establish relations between inputs and outputs (net energy) and thus to facilitate [[certification]], [[wikt:Special:Search/marking|marking]], and [[label]]ling, comparable characterizations, [[coefficient of performance]], energy resource planning, environmental impact assessments, meaningful energy statistics and forecasting of the direct natural energy resource or energyware inputs, technical energy system investments and the performed and expected future energy service outputs.<ref name="Grobe"/>

In ISO 13602-1:2002, [[renewable resource]] is defined as "natural resource for which the ratio of the creation of the natural resource to the output of that resource from nature to the technosphere is equal to or greater than one".

===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}}