Energy efficiency

From Exampleproblems

For energy efficiency in relation to economics, see energy conservation

In physics and engineering, including mechanical and electrical engineering, energy efficiency is a dimensionless number, with a value between 0 and 1. The energy efficiency of a process is defined as:

where W is the amount of useful work done by the process (in joules), and "energy" is the quantity of energy (again, in joules) used to run the process.

An efficiency of 1 (100%) is impossible — the second law of thermodynamics prohibits it. Theoretically, the mutual annihilation of matter and antimatter would be completely efficient, but the collection of the released energy would not be.fr:Efficacité énergétique sl:Izkoristek