How is the efficiency of a lamp measured?

The efficiency of a lamp is measured in lumens per watt, which quantifies how much light (in lumens) a lamp produces for each watt of energy it consumes. This metric reflects the lamp's effectiveness in converting electrical energy into visible light, allowing consumers and professionals to assess how energy-efficient a lighting option is. A higher lumens-per-watt ratio indicates a more efficient lamp, as it provides more light output for less energy usage.

Watts alone measure the power consumption of the lamp but do not account for how much light is produced. Lumens measure the amount of light emitted, which is essential for understanding brightness but not efficiency. Similarly, measuring watts per square foot is a method related to lighting design and energy usage in a given area, rather than assessing the efficiency of the light source itself. Thus, lumens per watt is the most relevant and effective measure for gauging the efficiency of a lamp.