Which statement about high EROEI is true?

• A. A high EROEI means more net energy available for society.
• B. A high EROEI means less net energy available for society.
• C. A high EROEI means higher emissions per unit energy.
• D. A high EROEI means energy is free.

Answer: (A)

The main idea tested is how Energy Returned on Energy Invested (EROEI) reflects the amount of energy left for society after covering the cost to obtain it. A high EROEI means you get a lot more energy out relative to what you had to put in, so the net energy available for other uses is larger. Net energy equals energy obtained minus energy invested, so when the ratio is high, the subtraction leaves a bigger surplus for electricity, heat, manufacturing, and other societal needs. For example, if you obtain 100 units of energy and only spend 10 units to extract and deliver it, you have 90 units of net energy (EROEI of 10). If another source also gives 100 units but requires 90 units to produce, you only have 10 units of net energy (EROEI around 1.1). That contrast shows why a high EROEI translates into more energy available for society.

This concept doesn’t automatically dictate emissions or cost in general. Emissions per unit energy depend on the fuel and technology used, not on the EROEI value itself. Similarly, a high EROEI doesn’t mean energy is free; there are still ongoing costs and investments, but a larger share of the produced energy can be used for societal needs rather than just recouping the energy invested.