Efficacy (lumen/Watt, lm/W)

Luminous efficacy measures how efficiently a light source converts electrical power into visible light. It is expressed in lumens per watt (lm/W). For example, if a lamp produces 1,000 lumens while using 10 watts of power, its efficacy is 100 lm/W. A higher efficacy means more light is produced for the same energy consumption, which is crucial for reducing running costs and meeting energy efficiency standards. Modern LEDs can achieve far higher efficacies than older technologies like incandescent or halogen lamps, making them the preferred choice in most applications.

Think: Light output per one energy unit