Wattage, Lumen, and Lux
These terms are to deal with the power and effectiveness of light sources.
Wattage (measured in Watts) is the power required to operate a light fitting. It refers to the total electricity that is consumed which will include:
The heat generated by the light source.
Operational aspects depending on the type of lighting device(such as gear control).
The energy of the light emitted from the bulb or tube.
The lumen (lm) is a standardised unit of measurement of the total amount of light (packets or quanta) that is produced by a light source, such as a bulb or tube. This total amount of light may also be referred to as “luminous flux”
Lux is a standardised unit of measurement of the light intensity (which can also be called “illuminance” or “illumination”) - as an example for reference purposes - 1 lux is equal to the illumination of a surface one metre away from a single candle.
Some examples and comparisons;
Wattage (measured in Watts) is the power required to operate a light fitting. It refers to the total electricity that is consumed which will include:
The heat generated by the light source.
Operational aspects depending on the type of lighting device(such as gear control).
The energy of the light emitted from the bulb or tube.
The lumen (lm) is a standardised unit of measurement of the total amount of light (packets or quanta) that is produced by a light source, such as a bulb or tube. This total amount of light may also be referred to as “luminous flux”
Lux is a standardised unit of measurement of the light intensity (which can also be called “illuminance” or “illumination”) - as an example for reference purposes - 1 lux is equal to the illumination of a surface one metre away from a single candle.
Some examples and comparisons;
- Outdoor average sunlight ranges from 32 000 to 100 000 lux
- At sunset and sunrise (with a clear sky), ambient outdoor light is about 400 lux
- Moonlight represents about 1 to 3 lux
- Warehouse aisles are lit to approx 160 lux
- Offices require about 240 lux
- Building corridors can be lit adequately at around 80 lux
- Typical home lighting is approx 240 lux
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Lighting examples
High Bay example A 400W Metal Halide lamp (458W including the control gear) - for high bay warehouse lighting: 30,000 lm, - approx 75 lm/W (lumens/watt) - at a 6m height from the lit area produces 175 lux over a 5.8m diameter area A 200W LED lamp (is rated at 200W including the control gear) - for high bay warehouse lighting: 17,800 lm, - approx 87 lm/W (lumens/watt) and - at a 6m height from the lit area produces 260 lux over a 5.8m diameter area Back to Top Tube light example A 36W T5 or T8 Fluorescent tube (plus either 1W for electronic, or 6W for low loss magnetic control gear) - for office ceiling lighting - 2100 lm, - approx 50 lm/W (lumens/watt) - at a 2m height from the lit area produces centre 95 lux, left or right by 1m 70 lux, left or right by 2m 42 lux An 18W T5 or T8 LED tube (is rated at 18W including the control gear) - for office ceiling lighting - 1550 lm, - approx 86 lm/W (lumens/watt) - at a 2m height from the lit area produces centre 92 lux, left or right by 1m 72 lux, left or right by 2m 40 lux Back to Top Bulb style example
A 75W Incandescent bulb - for general and task lighting: 750 lm - approx 10 lm/W (lumens/watt) and - at a 2m height from the lit area produces 150 lux A 50W Halogen bulb (240Vac) - for general and task lighting: 750 lm - approx 15 lm/W (lumens/watt) and - at a 2m height from the lit area produces 200 lux A 35W Halogen bulb (12Vac) (plus either 1W for electronic, or 6W for low loss magnetic control gear) - for general and task lighting: 525 lm - approx 15 lm/W (lumens/watt) and - at a 2m height from the lit area produces 145 lux A 7W Compact Fluorescent (CFL) bulb - for general and task lighting: 380 lm - approx 55 lm/W (lumens/watt) and - at a 2m height from the lit area produces 185 lux A 3W LED bulb (12Vac) (plus 1W for electronic control gear) - for general and task lighting: 320 lm - approx 87 lm/W (lumens/watt) and - at a 2m height from the lit area produces 195 lux |
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