Watt and Lumen

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There is a big difference between laboratory lighting performance of a led chip up to 100lm/w and the same Led mounted on a Pcb with voltage regulation, in a 40°C ambiant air in a downlight. The best Led bulb manufacturers are obtaining 75lumen/watt in warm white. Any claimed performance other this figure , especially in Warm White is just a a joke . Same for announced energy savings greatter tahn 5 times halogene bulbs.

The second big difference is traditionnal light is sent all around the bulb, when led light is sent in a specific direction in a 120° beam with the new smd chips . For a bulb used in a table lamp, this 360° spreading is perfect, but when then bulb is installed in a downlight it causes big efficiency losses.

50% of traditionnal bulb light is sent to the back ( ceiling direction) , and only 50 % of this amount is reflected back to the floor. The overall efficiency is around 70% with a good reflector, and you must add a good 30% loss if fixture have a sanded glass in the front. This the reason why a 140 lumens 10W halogen donwlight give the same light flux a 100 lumen led donwlight.


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