Nate Hagens describes 'EROI' (Energy Return on Investment) as a pivotal metric in understanding energy economics and sustainability. Hagens elaborates that EROI measures the ratio of the amount of usable energy obtained from a particular energy resource to the amount of energy expended to obtain that energy. He emphasizes that a high EROI indicates a more efficient and viable energy source, suggesting that it provides significantly more energy than what is necessary to produce it. Conversely, a low EROI signals diminishing returns, where nearly as much energy is spent in the extraction and processing as is gained. Hagens highlights that society’s complex infrastructure and economic stability are heavily influenced by the EROI of its primary energy sources, with declining EROI potentially leading to economic challenges and necessitating shifts in energy strategies and consumption patterns.

See also: exponential growth, ecological footprint, renewable energy, nuclear power, fossil fuel