Luminous efficiency, light efficiency for short. It is the ratio of luminous flux emitted by electric light source to its electric power consumption, and the unit is lumen/watt (lm/W), which is the most important technical parameter to evaluate the electric efficiency of electric light source. Luminous flux refers to the amount of light radiation per unit time, expressed in lumens. The greater the luminous flux per unit electric power used by the light source, the higher the efficiency of converting electric energy into light energy, that is, the higher the light efficiency.