Efficiency

Efficiency measures the fraction of the total input energy that is transferred usefully. A more efficient motor transfers a larger proportion of its input to lifting the load and a smaller proportion to unwanted outputs. Wasted energy has not disappeared or been destroyed; it has been transferred into less useful stores.

The units cancel, so efficiency has no unit. It can be expressed as a decimal between 0 and 1, or as a percentage by multiplying the decimal by 100.