EROEI = Usable Acquired Energy / Energy Expended It seems so simple. If the amount of energy produced relative to the amount of energy utilized in producing that energy tends to decline, at some point as the ratio approaches 1.0 (or perhaps even becomes a fraction less than 1.0) there is little if any return on the energy invested and society will collapse. But is this concept really workable and useful? There are many issues related to how this ratio (sometimes abbreviated as EROI) is calculated. This affects both the numerator and the denominator of the ratio. The first problem is that this equation is usually interpreted as being the useful acquired energy divided by the useful energy expended. Energy expended is usually limited to something you would miss if it became unavailable. This means you do not count the energy from the sun that is used to make […]