The ratio of energy delivered by an energy source to the energy invested in obtaining it. A high EROI means the source delivers a large net energy surplus available for economic work. A low EROI approaches a “net energy cliff” at which additional exploitation of the source yields little or no surplus.
The relevant measurement for economic analysis is the finished-fuel (final-stage) EROI rather than the well-head figure. At the finished-fuel stage, global fossil-fuel EROI is about 6 to 1 and declining (Brockway et al., Nature Energy, 2019). Earlier well-head measurements had reported much higher figures: global oil-and-gas EROI for publicly traded companies fell from 30 to 1 in 1995 to about 18 to 1 by 2006 (Gagnon et al. 2009). The physical significance is that each unit of societal energy surplus, the basis of growth in the industrial S-curve, is shrinking.
Related terms
Sources
- Brockway et al. (2019). Estimation of global final-stage EROI for fossil fuels. Nature Energy
Provenance
Standard technical term in energy economics; used here in the sense established by Brockway et al. (2019).