What does the word efficiency mean when you talk about energy?

Answer 1

It is accepted that within the universe energy is never created or destroyed; in any process it is simply converted from one or more types of energy to one or more other types.

A process is carried out with the intention of utilising one or more desired types of energy converted from others. Efficiency is the quantification of how successful that conversion is.

'Efficiency' being the proportion of desired energy obtained, 'energy loss' (which is technically incorrect) is the proportion of resulting energy arising in unwanted forms.

There are eight fundamental types of energy - light, sound, heat, electric, kinetic, gravitational, chemical, elastic.

A car engine uses the chemical energy in petrol to create the desired kinetic (movement) energy. In doing so the internal explosion produces unwanted heat, light and sound. Friction in the moving parts also creates heat and sound. Movement of the moving parts uses kinetic energy which reduces the amount available to move the car. Unburnt petrol is expelled into the atmosphere and retains unreleased chemical energy. Efficiency in this example is the proportion of kinetic energy derived from the petrol used.

Answer 2

Efficiency in energy terms refers to how effectively energy is converted from one form to another or how well it is used in a process. It is a measure of the total useful energy output compared to the total energy input. A higher efficiency indicates that less energy is wasted during the conversion or usage process.