Net energy gain

It is also possible to overcomplicate the equation by an infinite number of externalities and inefficiencies that may be present during the energy harvesting process.

To better understand this, assume an economy has a certain amount of finite oil reserves that are still underground, unextracted.

For instance, in the Athabasca Oil Sands, the highly diffuse nature of the tar sands and low price of crude oil rendered them uneconomical to mine until the late 1950s (NEG<0).

In all energy extraction cases, the life cycle of the energy-extraction device is crucial for the NEG-ratio.

Net energy gain of biofuels has been a particular source of controversy for ethanol derived from corn (bioethanol).

ISO 13602-1 provides methods to analyse, characterize and compare technical energy systems (TES) with all their inputs, outputs and risk factors.