Lighting efficacy
Rules of Thumb, Guidelines for building services (5th Edition) BG 9/2011, by Glenn Hawkins, published by BSRIA in 2011, defines lighting efficacy as: ‘The amount of light (luminous flux) produced by a light bulb or other light source, usually measured in lumens, as a ratio of the amount of power consumed to produce it, usually measured in watts.’
BG 87/2024, Useful Information Guide, written by Chin Hang “Kay” Lam and published by BSRIA in 2024, defines lighting efficacy as: ‘A measure of how much light a light source produces for the energy put in to it. This is normally expressed in lm/W (lumens per watt).’
--BSRIA
See also: Lamp efficacy.
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