Express efficiency as a percentage.

Efficiency is a measure of how well energy is converted from one form to another, expressed as a percentage. It is calculated by taking the useful energy output of a device or process and dividing it by the total energy input, then multiplying by 100. This percentage indicates the proportion of energy that is effectively used for the intended purpose, with the remainder often being lost as wasted energy. Understanding efficiency helps in evaluating and improving energy use in various systems, highlighting the importance of minimizing energy losses to enhance overall performance.