How is luminaire efficacy calculated?
Emma Johnson
Updated on May 04, 2026
Luminaire efficacy is the ‘Light output of an entire luminaire divided by the total power consumed by the lamps and ballasts. Equal to the lamp efficacy multiplied by the light output ratio of the luminaire. ‘ It is expressed in lumens per Watt (lm/W).
Which of the following luminaires has the highest efficacy?
683 lm/W
The highest perception of brightness experienced by the human eye is generated with green light on the 555 nm wavelength. The greatest luminous efficacy which can theoretically be achieved at 555 nm is, altogether, 683 lm/W. In this context the expert refers to the »photometric radiation equivalent Km«.
How do you calculate efficacy?
Efficacy is calculated by dividing the fixture lumens by the total fixture wattage consumed. 2066 lumens/50 watts = 41.32 lumens per watt.
What is efficacy formula?
In science, efficacy is a quantity of measurement for light sources and is described as the ratio of luminous flux to power (lm/W). The equation will be efficacy = luminous flux / power. The SI unit for the result will be lm/W.
How do you solve efficacy?
The higher the efficacy, the more money you’ll save. Make a note about the formula you will use. The equation will be efficacy = luminous flux / power. The SI unit for the result will be lm/W.
What is luminaire efficacy?
Luminaire efficacy refers to how efficient the entire lighting fixture is. It measures the efficiency ratio of the total amount of lumens output by the luminaire to the amount of electricity required to power the light fixture.
What is the efficacy of a halogen lamp?
The luminous efficiency of halogen lamps cradles between the previous two at an approximate 3.5 percent efficiency. Luminous efficiency is one way to determine which bulb to choose, yielding CFLs as the most efficient, followed by halogen bulbs and then incandescent bulbs.
What is efficacy and how is it calculated?
This is calculated by comparing the number of cases of disease in the vaccinated group versus the placebo group. An efficacy of 80% does not mean that 20% of the vaccinated group will become ill. Vaccine effectiveness is a measure of how well vaccines work in the real world.
What is the value of efficacy of halogen lamp?
Examples
| Category | Type | Overall luminous efficacy (lm/W) |
|---|---|---|
| Halogen incandescent | Halogen-IR (120 V) | 17.7–24.5 |
| Tungsten quartz halogen (12–24 V) | 24 | |
| Photographic and projection lamps | 35 | |
| Light-emitting diode | LED screw base lamp (120 V) | 102 |
