The energy transition isn’t just sounding the death knell for fossil fuels. According to some experts, it has also revealed flaws in an idea that has bugged some academics for decades: As we move to less energy-dense fuels, could we end up without enough surplus for society?
At the heart of this debate is one of the most important physical metrics you’ve never heard of: energy return on investment, or EROI.
Devised in the 1980s by systems ecologist Charles A.S. Hall and others, the basic principle behind EROI, also called energy returned on energy invested, is simple: A source of energy is only useful if you can get more energy out of it than what you put in.
