In this article I will show that ERoEI is almost totally unimportant by itself. It does not matter if ERoEI is increasing or decreasing. ERoEI provides no guidance about which sources of energy we should pursue, nor does it offer any guidance about how much net energy will be available to us in the future. By itself, ERoEI is a useless figure. Although different sources of energy (such as coal or solar PV) have different ERoEI ratios, this means nothing important. What is important to civilization (and to us) is the amount of net energy obtained from a source of energy, not its ERoEI. The two are not the same. It is the amount of net energy which determines how much we can drive, whether we can take long airplane trips, and so on. Unfortunately, the amount of net energy from a source cannot be determined from its ERoEI. […]