Haitz's law

Haitz's law is an observation and forecast about the steady improvement, over many years, of light-emitting diodes (LEDs).

Illustration of Haitz's law. Light output per LED package as a function of time, note the logarithmic scale on the vertical axis.

It claims that every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor of 20, for a given wavelength (color) of light. It is considered the LED counterpart to Moore's law, which states that the number of transistors in a given integrated circuit doubles every 18 to 24 months.[1] Both laws rely on the process optimization of the production of semiconductor devices.

Haitz's law is named after Roland Haitz (1935–2015),[2] a scientist at Agilent Technologies among others. It was first presented to the larger public at Strategies in Light 2000, the first of a series of annual conferences organized by Strategies Unlimited.[3] Besides the forecast of exponential development of cost per lumen and amount of light per package, the publication also forecast that the luminous efficacy of LED-based lighting could reach 200 lm/W (lumen per Watt) in 2020, crossing 100 lm/W in 2010. This would be the case if enough industrial and government resources were spent for research on LED-lighting. More than 50% of the electricity consumption for lighting (20% of the totally consumed electrical energy) would be saved reaching 200 lm/W. This prospect and other stepping-stone applications of LEDs (e.g. mobile phone flash and LCD-backlighting) led to a massive investment in LED-research so that the LED efficacy did indeed cross 100 lm/W in 2010. If this trend continues, LEDs will become the most efficient light source by 2020.

The theoretical maximum for a continuous wavelength (as opposed to one made up of a combination of discrete-wavelength sources) white light source (at 5800K colour temperature with wavelengths restricted to the visible band of between 400nm and 700nm) is 251 lm/W.[4] However, some non-continuous wavelength composite "white" LEDs have achieved efficacies of over 300 lm/W.[5][6]

In 2010, Cree Inc., developed and marketed the XM-L LED that claimed 1000 lumens at 100 lm/W efficacy and 160 lm/W at 350 mA and 150 lm/W at 700 mA.[7] They also claimed to have broken the 200 lm/W barrier in R&D with a prototype producing 208 lm at 350 mA.[8] In May 2011, Cree announced another prototype with 231 lm/W efficacy at 350 mA.[9] In March 2014, Cree announced another prototype with a record-breaking 303 lm/W efficacy at 350 mA.[5]

In 2017, Philips Lighting started offering consumer LED lights with 200 lm/W efficacy in Dubai[10] using LED filament technology, 3 years before what Haitz's law predicted.