AP Environmental Science

Answer: A - Energy efficiency is the measure of the useful energy produced compared to the energy that is actually consumed.

Key Takeaway: Energy efficiency is a very important topic, due to its direct effects upon conservation and sustainability. Energy efficiency measures the useful energy produced compared to the actual energy that is consumed. A prime example of this is a light bulb. In a light bulb, the light is useful energy, but the heat is wasted. Thus, incandescent light bulbs, which do not produce the sheer amount of heat that regular bulbs produce, are much more efficient.