energyreturn

Energy return, or energy return on investment (EROI), is a metric used to evaluate the efficiency of energy production. It expresses the ratio of usable energy a resource delivers to the amount of energy required to obtain that energy. The concept helps gauge the long-term viability and economic profitability of energy sources.

Calculation depends on the system boundaries chosen. EROI = energy produced divided by energy invested. Inputs can include exploration, extraction, processing, manufacturing of equipment, construction, transmission, maintenance, and decommissioning, while outputs are the usable energy delivered to end-use or the grid. Time horizon and energy quality influence the value; high-grade energy is more valuable than low-grade energy but may be counted equally in the ratio.

Representative ranges vary by technology and location. Conventional oil historically showed high EROI in earlier decades, though modern extraction can be lower. Coal and natural gas often yield higher EROI than some renewables, but this depends on resource quality and lifecycle assumptions. Wind and solar photovoltaic EROI estimates commonly range from roughly 6:1 to 12:1 for solar and 20:1 to more than 50:1 for wind, depending on location, technology, and boundaries. Nuclear and hydroelectric resources also show variable EROI values. Bioenergy tends to be highly variable due to feedstock and conversion pathways.

Limitations include sensitivity to boundary definitions, neglect of economic costs and externalities, and failure to capture grid reliability or environmental impacts. As technology and energy systems evolve, EROI estimates change and should be interpreted relative to context and objective.