The term efficacy stands for effectiveness or efficiency. In lighting technology, the term is used for luminous efficacy or lighting efficiency. It is the quotient of the luminous intensity emitted by a light source and the power supplied to this light source.
Luminous efficacy is expressed in lumens per watt( lm/W) and thus corresponds to luminous efficacy. The efficacy value indicates the luminous flux emitted by a light source when it is supplied with one watt (W) of power. The luminous efficacy is mainly specified for light-emitting diodes.
The luminous efficacy of high-power LEDs currently exceeds 250 lm/W, while that of OLEDs reaches values of between 300 lm/W and 400 lm/W. In comparison, energy-saving lamps are around 60 lm/W, halogen lamps around 90 lm/W and incandescent lamps around 15 lm/W.