Which statement about EROI interpretation is true?

• A. EROI equals energy invested divided by usable energy obtained.
• B. EROI equals usable energy obtained divided by energy invested; higher values indicate more favorable energy sources.
• C. EROI measures only the environmental impact.
• D. EROI must always be less than 1 for viable energy sources.

Answer: (B)

ER OI is the ratio of energy you get back from a source to the energy you had to invest to obtain it. It’s calculated by dividing the usable energy obtained by the energy invested, so a larger number means more energy is produced per unit of energy spent. This is why higher EROI values indicate a more favorable energy source—the more energy you recover for each unit you spend, the more efficient the overall energy process is. It’s not a measure of environmental impact, and viable energy sources must have an EROI greater than 1, since you need to produce more energy than you put in.