Luminous efficacy

Unit of measurement: lumens per watt [lm/W]
Luminous efficacy indicates the efficiency with which the electrical power consumed is converted into light. It is measured in lumens per watt (lm/W). The luminous efficacy of conventional incandescent lamps (such as R5 W) is typically 10 lm/W, that of tungsten-halogen lamps (such as H7) 26 lm/W, and that of gas discharge lamp (such as D2S) 91 lm/W.