Luminance Efficacy is the ratio of luminous flux to power. The SI unit is lm/W. A distinction should be drawn between this and Luminance efficiency, which is a percentage.

Examples

• Candle: 0.3 lm/W; efficiency: 0.04%
• 500W tungsten halogen : 19.8 lm/W; efficiency: 2.9%
• White LED w/o PSU: 4.5-150 lm/W; efficiency: 0.66-22%
• Xenon discharge lamp: 30-50 lm/W; efficiency: 4.4-7.3%
• T8 fluorescent tube: 80-100 lm/W; efficiency: 12-15%
• Ideal - green light at 555nm: 683.002 lm/W; efficiency: 100%

See also

Post on an LED record of 208 lm/W

• Discussion