Lighting efficacy compares luminous output with input power.
Efficacy is usually expressed in lumens per watt. It helps compare light output against electrical input for the same type of lighting task.
Technical meaning
Lighting efficacy is the ratio between luminous output and input power, usually written as lumens per watt.
The number is most useful when comparing fittings with the same output basis, similar beam role and similar visual task.
Lumens per watt relationshipEfficacy compares output with input power; it does not replace colour, glare or distribution checks.
Calculation use
Efficacy supports LED replacement checks by separating the output question from the load question.
Energy comparisons can show lower annual kWh while the lighting note still checks maintained lux, beam spread and colour quality.
Not the same as
Efficacy is not a full quality score. CCT, CRI, glare, dimming behaviour and optical distribution still matter.
Efficacy is not a maintained-lux result. A high lm/W fitting can perform poorly if the distribution or spacing does not suit the surface.
Australian context
Australian LED retrofit notes should keep efficacy, luminaire output, connected load and Energy Rating/GEMS-related cautions distinct from model selection.
Examples
Example
Value
Planning note
900 lm at 10 W
90 lm/W
A basic output-to-load ratio before optical checks.
1,600 lm at 14 W
114 lm/W
Higher efficacy does not settle beam spread or glare.
Old load versus LED load
kWh change
Energy savings need operating hours and the entered tariff.
Efficacy is a calculation ratio. Regulated lamp and LED information should be read through current Energy Rating and GEMS material where it affects claims.