Efficiency and operational parameters

Typical indicator LEDs are designed to operate with no more than 30-60 milliwatts [mW] of electrical power. Around 1999, Philips Lumileds introduced power LEDs capable of continuous use at one watt [W]. These LEDs used much larger semiconductor die sizes to handle the large power inputs. Also, the semiconductor dies were mounted onto metal slugs to allow for heat removal from the LED die.

Typical indicator LEDs are designed to operate with no more than 30–60 milliwatts [mW] of electrical power. Around 1999, Philips Lumileds introduced power LEDs capable of continuous use at one watt [W]. These LEDs used much larger semiconductor die sizes to handle the large power inputs. Also, the semiconductor dies were mounted onto metal slugs to allow for heat removal from the LED die.
One of the key advantages of LED-based lighting is its high efficiency, as measured by its light output per unit power input. White LEDs quickly matched and overtook the efficiency of standard incandescent lighting systems. In 2002, Lumileds made five-watt LEDs available with a luminous efficiency of 18–22 lumens per watt [lm/W]. For comparison, a conventional 60–100 W incandescent light bulb produces around 15 lm/W, and standard fluorescent lights produce up to 100 lm/W.

In September 2003, a new type of blue LED was demonstrated by the company Cree, Inc. which produced a commercially-packaged white light giving 65 lm/W at 20 mA, becoming the brightest white LED commercially available at the time and more than four times as efficient as standard incandescent.

In 2006 they demonstrated a prototype with a record white LED luminous efficiency of 131 lm/W at 20 mA. Also, Seoul Semiconductor has plans for 135 lm/W by 2007 and 145 lm/W by 2008, which would be approaching an order of magnitude improvement over standard incandescent and better even than standard fluorescents. Nichia Corporation has developed a white light LED with luminous efficiency of 150 lm/W at a forward current of 20 mA.[20]

It should be noted that high-power (≥ 1 W) LEDs are necessary for practical general lighting applications. Typical operating currents for these devices begin at 350 mA. The highest efficiency high-power white LED is claimed by Philips Lumileds Lighting Co. with a luminous efficiency of 115 lm/W (350 mA).

Cree issued a press release on November 19th, 2008 about a laboratory prototype LED achieving 161 lumens/watt at room temperature. The total output was 173 lumens and the correlated colour temperature was reported to be 4689 K