LED Efficacy

White light-emitting diodes are today already the most efficient commercial light sources available used for regular lighting tasks. But even with this technology there are vast differences. Not only between the various types that are offered by different manufacturers, but also in terms of the light generation type itself. In general, the higher the power of the individual LEDs, the lower the efficiency. And the colder the light colour, the higher the efficiency. Over the last few years, there has been a reduction in the impact of the light colour on the luminous flux. In the case of good, reputable manufacturers the luminous flux of a warm white LED is only 4-5% less than with the same type of cold white LED. The power has a greater influence. The most efficient white LEDs of mid-power class (approx. 0.2 W) available today (status: Mid 2015) produce a luminous efficiency of up to 180 lumens/watt if they are operated in ideal conditions. By comparison, the current 2W light-emitting diodes from leading manufacturers only reach a luminous efficiency of around 145 lm/W. This is already a difference of 20%. The LED matrix modules of up to 150 W only reach around 110-120 lm/W.

Irrespective of these differences, the same applies to all light-emitting diodes: we are still seeing a marked increase in the efficiency. It is unlikely that 5 years ago anybody would have expected the luminous efficiency of 80 lm/W of those days to increase to almost 200 lm/W of today in such a short period of time. And development is continuing to advance. Realistically we must assume that we are fast approaching the physical limit of approx. 250 lm/W (cold white LED).