U.S. Department of Energy defines lighting application efficiency as:
the delivery efficiency of light from the light source to the lighted task. It can also consider the effectiveness of the light spectrum for the lighting application, and the ability to actively control the source to minimize energy consumption when the light is not being used. Improved optical design can allow more efficient delivery of light with the optimum optical distribution. Precise spectral control enables delivery of more suitable light for the application needs and buildings occupants. Instantaneous control over a wide range of intensity provides the ability to deliver the right amount of light on demand.