Total lumen output of a luminaire expressed as a percent of rated bare lamp lumens, as determined by photometric tests.
The ratio of the light emitted by a luminaire to the light emitted by the lamp or lamps within it. Components of a luminaire such as reflectors and diffusers absorb some of the light from the lamp(s). A highly efficient luminaire emits most of the light that the lamp(s) emits.
The ratio of total lumen output of a luminaire and the lumen output of the lamps, expressed as a percentage. For example, if two luminaires use the same lamps, more light will be emitted from the fixture with the higher efficiency.