The luminous efficacy of a light source can be simply explained as the light source’s lumen value against its energy consumption, Luminous efficacy is a part of a lights Energy effectiveness, it appropriates power supply in lumens per watt (lm/W), it includes the optical efficiency of the luminaire or light fixture, and how well the luminaire delivers light to the target area without casting light in other directions.

The luminous efficacy of a typical incandescent bulb is 16 lumens per watt, while a Compact fluorescent bulb or CFL gives 60 lm/W and 150 lm/W for some white LED lamps and LED Bulbs.