Luminous efficacy h

Unit of measurement: lumen per watt [lm/W]:
Luminous efficacy h indicates the efficiency with which the electrical power consumed is converted into light. The maximum that can be achieved in theory, with all the energy being converted into visible light, is 683 lm/W. In reality, the figures are much lower, between 10 and 150 lm/W.

Luminous efficacies of various light sources