How efiicient are white LEDs?

The declared luminous efficiency of white LED light is systematically growing from year to year. Under laboratory conditions the highest light efficiency values for white color diodes exceeds 170lm/​W. It is worth mentioning that the laboratory data for LEDs does not have any reflection to the real working conditions, so we cannot go by it. Nowadays diodes generating white light with luminous efficiency of 100lm/​W are available on the market(catalogue data for LED is given for the junction p-​n temperature of 25 degrees C).

The lighting efficiency of LED depends on work conditions, mainly temperature. Some LED and LED modules manufacturers declare data for optimal working conditions, which that can be hardly achieved in practical usage, so given data can be unrealistic. The resulting efficiency of LED may be also affected by some other factors as: power supply efficiency, optical system efficiency, loses resulting from additional elements, etc.. What is more, light conversion in phosphor causes a loss of energy (known as Stokes shift), when phosphor conducts the conversion of wavelength from the shorter to longer one that reduces the overall LED efficiency.