What is the formula for calculating energy efficiency?

The formula for calculating energy efficiency provides a clear measure of how well energy is converted from one form to another while minimizing waste. The correct formulation states that energy efficiency is determined by comparing the useful energy output to the total energy input, which is expressed as:

Energy efficiency (in percent) = (useful energy out / energy in) x 100.

This calculation is essential in evaluating how effectively an energy system, such as a machine or appliance, operates. A higher percentage indicates that a larger proportion of the input energy is converted into useful work rather than being dissipated as waste energy. This concept is crucial in energy management and conservation, as it encourages designs and technologies that maximize efficiency, reducing both energy costs and environmental impact.

Understanding this principle allows for informed decisions in various fields, including engineering, economics, and environmental policy, to promote sustainability and optimize energy use.