"The Energy Return on Investment" (academic paper)

"The Energy Return on Investment" (EROI) is a measure of how much useful energy we get from an energy-producing activity compared to the amount of energy we need to invest to produce it. For example, if it takes the energy equivalent of one barrel of oil to extract five barrels from a well, the EROI is five: meaning we gain five units of energy for every unit invested. A higher EROI indicates a more efficient process, providing more net energy for society’s needs. EROI helps assess the sustainability and economic viability of different energy sources over time.