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.
[edit] Related articles on Designing Buildings
Featured articles
Check out some of the best features and news from Designing Buildings as well as key stories from around the web.
CIAT confirm the winners of the 2026 architectural technology awards.
Government launches a one stop shop for flood preparedness.
Sir Edwin Lutyens: Britain's greatest architect? Book review.
CIOB publishes free template to help assess and manage risks.
ECA's reflections on Party Conference season
Burnham wants to be confident of winning before asking for a fresh mandate.
New Chief Construction and Scientific Adviser
Sergio Cavalaro, Professor of Infrastructure Systems at Loughborough University.
Building safety levy for England
CIAT publish estimator tool for members.
Water sector faces a growing crisis that could slow the delivery of vital infrastructure.
Undervaluing our industrial past
Heritage value changes as taste for building styles changes.
Changing expectations around competence and compliance
New information sheet from CIAT.
Grenfell investigation files passed to CPS
Angela Rayner apologises on behalf of the British state.
Electrical contractors need to understand the practical implications.