About the Efficiency Calculator

Efficiency compares useful work to total energy supplied: η = output ÷ input. The difference between the two — energy that cannot be recovered — is almost always lost as heat. For 800 J of useful work from 1000 J of input, efficiency is 80% and 200 J are wasted.

Efficiency in Context

Engineering decisions hinge on this ratio: replacing a 30%-efficient gasoline engine with an 85% electric motor cuts energy use by more than half. But efficiency is a system property — motors, drivetrains, and charging multiply together, so each stage must be efficient for the total to be.