One of the ways — if not the best way — to track the progress of LEDs over the past few years has been through the metric of lumens-per-watt. As you can gather from the name this is an efficiency rating that is based on the amount of visible light emitted relative to the amount of power consumed. A lumens-per-watt (lpw) rating is especially interesting because it works regardless of the light source — the lpw rating for an incandescent bulb is a lowly 15 (or so) while newer LED bulbs are in the range of 75. While 75 lpw is plenty efficient, it’s no where near what manufacturers like Cree are working on. In fact, the company has just put out a 200 lpw LED known as the XLamp MK-R.

Back in February 2010 the company had a 208 lpw LED operating in its labs, meaning it took the company close to two years for the technology to make its way into production. While that is surely an excellent turn around time, it’s worth noting that the MK-R only achieved this rating while operating at 1W and 25 degrees Celsius (77F) — 25C being room temperature, while the LEDs themselves are capable of operating without problems at 4x that level.

At higher temperatures LEDs do experience a drop in lumen production, though. Running at 85C — a typical temperature — the quad-die MK-R puts out 106.7 lpw (1600 lumens at 15W). Some of the other variants of the MK-R (different bins) are capable of slightly higher numbers, though that’s happening at higher color temperatures and lower CRIs, which means bluer, less accurate light overall.

If this is starting to smell funny, don’t worry: things probably aren’t as bad as you think. After the big 200 lpw announcement, Cree explained that this makes the “next generation of 100+ lumens-per-watt system[s]” possible, meaning that it understands that no one will see that sort of efficiency in real-life applications for some time, but buyers will get 100+ lpw fixture options. And more efficiency means less power and brighter LEDs, which means energy savings and cheaper upgrades. So that halogen replacement your business was looking to do makes more sense than ever.

Followers of lighting, while impressed with the advance, probably won’t be shocked. LEDs have their own version of Moore’s law, known as Haitz’s law, which forecasts that LEDs will see the same sort of exponential growth seen in transistors counts. (Both LEDs and computer chips being based on semiconductor technology.)

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