What is defined as the ratio of useful energy output to total energy input?

The concept defining the ratio of useful energy output to total energy input is known as energy efficiency. Energy efficiency measures how effectively energy is used to perform a specific task or produce a desired output. It quantifies how much of the energy consumed is converted into useful work or output, rather than being wasted in the process.

For example, if a device uses 100 units of energy and converts 80 of those units into useful work, its energy efficiency would be 80%. High energy efficiency means that less energy is wasted, which is beneficial for both economic and environmental reasons, as it often results in reduced energy consumption and lower emissions.

Understanding this concept is crucial when evaluating different technologies or methods for energy production and consumption, as it directly impacts sustainability and resource management in the context of energy use.