luminous efficacy of a source

[3.11]

The total emitted luminous flux divided by the total source electrical input power; expressed in lumens per watt (lm/W).

Note 1: The term luminous efficacy can be applied to a single component, multiple components, or component(s) plus any associated electrical control equipment. The user will need to state the intended meaning. For example: lamp efficacy, luminaire efficacy, system efficacy (stating what the “system” is).

Note 2: Luminous efficacy as defined here is not to be confused with luminous efficacy of radiant flux.

NOTE: This term and its definition were changed in ANSI/IES RP-16-17 Addendum 4. Previously called luminous efficacy of a source of light.