Lamp efficacy
According to BRE’s The essential guide to retail lighting:
Lamp efficacy (or luminous efficacy) is ‘The ratio of the light output from a light source to the power consumed; measured in lumens per Watt (lm/W). The higher the efficacy value of a lamp or lighting system, the more energy-efficient it is.’
‘For example, the efficacy of a 60 W incandescent light bulb is 12 lm/W, and of an 11 W CFL (compact fluorescent lamp) is 55 lm/W. For a 36 W fluorescent tube it is 91 lm/W. This last figure is a lamp efficacy; it excludes the power consumed by the ballast that is needed to run the discharge lamps.’
Ballast or control gear, is ‘Part of the control equipment of fluorescent or discharge lamps, used to stabilise the current. The older, traditional main-frequency ballast can consume up to 20-25% of the total lamp current. A modern electronic ballast working at high frequency consumes about 30% less current, and can be used to regulate or dim the lamp output.’
See also: Lighting efficacy
[edit] Related articles on Designing Buildings Wiki
- Artificial lighting.
- Ballast or control gear.
- Colour appearance.
- Colour Rendering Index CRI.
- Daylight benefits in healthcare buildings.
- Daylight factor.
- Daylight lighting systems.
- Dichroic reflector.
- Discharge lamp.
- Extra-low voltage lamps.
- General lighting v task lighting.
- Illuminance.
- Lamps.
- Light pollution.
- Lighting.
- Lighting efficacy.
- Lighting energy numeric indicator LENI.
- Lighting of construction sites.
- Luminaire efficacy.
- Lux.
- Rights to light.
Featured articles
Check out some of the best features and news from Designing Buildings as well as key stories from around the web.
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.
The real barrier to getting more value from digital technology.
Your guide to The Construction Reset at UKCW Birmingham.
Accommodating the Victorian and Edwardian working woman. Book review.
Rethinking passive fire protection in design
PFP demands the same level of design rigour as structure or services.
38% of Gen Zs feel safe when a fire door is wedged open.
Stunning images from around the world
Shortlist for CIOB’s Art of Building photography competition.
Guidance for conversion of traditional pre-1919 stone buildings.