What is energy efficiency, and why is it important in energy planning?

• A. The ratio of useful work or heat output to total energy input; higher efficiency reduces energy waste, lowers costs, and lowers environmental impact.
• B. The ratio of total energy input to useful work output; higher input means more energy used.
• C. The ability to generate energy with no losses.
• D. The maximum possible energy output from a system.

Answer: (A)

Energy efficiency is the ratio of useful work or heat output to the total energy input. It shows how effectively energy is being used—when this ratio is higher, less energy is wasted as heat or other losses. In energy planning, boosting efficiency means you can achieve the same service with less energy, lowering operating costs, reducing energy demand, and cutting environmental impact. For example, better insulation, more efficient equipment, and heat recovery in processes let you get the same result with less energy. The other ideas misrepresent what efficiency means: simply increasing input for more output isn’t efficiency, and imagining no losses or a focus on maximum output ignores how much energy is wasted.