What does efficacy measure in lighting?

Efficacy in lighting refers specifically to the measure of how effectively a light source converts electrical energy into visible light, which directly relates to energy efficiency. It is quantified as the ratio of luminous output (measured in lumens) to power consumption (measured in watts). A higher efficacy indicates that a lighting source produces more light for less energy, making it more efficient.

Understanding efficacy is crucial for selecting light fixtures that not only meet illumination needs but also promote energy conservation. While color accuracy, light output, and brightness levels are important aspects of lighting design, they do not encompass the measure of efficiency in energy usage that efficacy provides. Therefore, emphasizing energy efficiency aligns perfectly with the definition of efficacy in lighting.