LED Lighting: Ready for Prime Time?

I know that I should be blogging about something of greater import, such as Sarah Palin or the current economic implosion. But I can’t really think of much to say that hasn’t already been bouncing around the media echo chamber. Anyway, several folks on my f’list and James Howard Kunstler have done a pretty awesome job on the latter. JHK’s take:

Last week's ripe moment turned out to be the Thursday night Washington photo op when Treasury Secretary Paulson and Fed Chief Bernanke emerged from a huddle with House Speaker Nancy Pelosi and just about every other legislative eminentissimo in an attempt to reassure the nation that its financial system had not turned into something like unto a truckload of stinking dead carp. I don't know about you, but I got two distinct vibes from the faces in that particular tableau: 1.) abject fear, and 2.) a total lack of conviction that they knew what they were doing.

Anyway, I wanted to write about light emitting diode (LED) lighting—it’s been touted as “the next thing after CFLs” for a while now. Last time I checked, they weren’t that much more efficient than CFLs, and really pricy. So I wanted to chew through the current numbers, look at the current prices, and see if I’ve been giving them a fair shake. One of the things that prompted me is that I saw a Department of Energy document “LED Basics”: LED technology continues to develop rapidly as a general light source. As more LED products and light fixtures are introduced on the market, what do retailers, energy efficiency advocates, and consumers need to know to make informed buying decisions?

As for background: I’ll assume my readers need no technical introduction to LEDs; I did a primer on lighting efficiency in my blog in 2006. In that post, I talked about efficacy (how lighting efficiency is described)—measured in lumens per watt (light units per electricity units). The Wikipedia table on efficiency ranges is worth repeating:

Incandescents: 12-18 lumens/Watt
Halogens: 16-25 lumens/Watt
Compact fluorescents: 45-60 lumens/Watt
Fluorescent tubes: 60-100 lumens/Watt
Light-emitting diodes: 60-100 lumens/Watt (with prototypes up to 150)

So what’s actually out there, on the market? Well, the Cree LR6 is about as perfect of a light as you can imagine. A writeup from Environmental Building News (”LED Downlight from LLF—Most Efficient on the Market”) has a pretty good description. It screws into a normal Edison base, works as a can downlight, gives equivalent light output of a 65 W incandescent for 12 watts, can be dimmed, and has a 92 CRI (color rendering index). For reference, incandescents are 95-100, most CFLs are hitting 82 nowadays; here are some typical values. And it’s available on the market now. Also, I’ve played with one of them—it looks good, and if you drop it on the floor, you’ll just dent your floor (it’s a great big aluminum heat sink with some solid state electronics inside).


Oh, and, it costs $90 to $150. Youch! Also, has an efficacy of 54 lumens per watt. For comparison, the CFLs that I am running in my house right now have an efficacy of 50-60 lumens per watt (light output declines with bulb life; lower end is the “average” figure).

To put it another way, the DOE document tries to put a good face on it, under “Are LEDs cost-effective?”: Costs of LED lighting products vary widely. Good quality LED products currently carry a significant cost premium compared to standard lighting technologies. However, costs are declining rapidly. In 2001, the cost of white light LED devices was more than $200 per thousand lumens (kilo-lumens). In 2007, average prices have dropped to around $30/klm.

For reference, 1000 lumens (or 1 klm) is about equivalent to a 75 W incandescent, or a 20 W compact fluorescent. I can get latter at Tag’s for about $5 (or $1, if you’re dorkily taking advantage of a sale)

A few more examples from Energy Federation Inc.--both of these are 12 V, so they don’t include the transformer needed to go from 120 V to 12 V:

Everlumen MR16; 45 lumens/watt, $55 (pin base—not screw base;12 V system)
Philips Color Kinetics MR16 8 lumens/watt, $59 (12 V system)


Now I’m not out to do a hatchet job on LEDs here—I really wish that this technology would take off. They have a better lifetime than CFLs (30,000 to 50,000 hours, vs. 8,000 to 10,000 hours), and they don’t have mercury. Why isn’t this technology kicking ass for general lighting yet? It appears that part of it is that while LEDs can make light very efficiently, making white/high color rendering index light is a bit more difficult:

The best white LED products can meet or exceed the efficiency of compact fluorescent lamps (CFLs). However, many white LEDs currently available in consumer products are only marginally more efficient than incandescent lamps. The best warm white LEDs available today can produce about 45-50 lumens per watt (lm/W). In comparison, incandescent lamps typically produce 12-15 lm/W; CFLs produce at least 50 lm/W. Performance of white LEDs continues to improve rapidly.

Anyway, I’ve seen LEDs used in specialized applications that make a lot of sense: exit signs, and traffic lights. After all, exit lights are typically running 24/7/365, which makes the energy payback that much faster; also, they’re typically in commercial buildings, where you have to factor in lamp replacement cost into your overall lifetime cost. Similar for LED traffic lights—although the Car Talk guys talk about one unforeseen consequence in a puzzler (answer here).

Aha—here’s a description from RPI’s Lighting Research Center: Primarily, these applications have taken advantage of the characteristics of LEDs that have made them most suitable for indication, not illumination. What is the difference between indication and illumination? Indication refers to the use of a light source that is to be viewed directly as a self-luminous object, such as in signs, signals, and indicator lights on electronic equipment. Examples of successful LED indication applications include exit signs and traffic signals. Illumination refers to the use of a light source to view other objects by the light reflected from those objects, such as the general lighting found in most rooms, or task lighting found on many desks.

Also:

LEDs are quite effective and efficient for colored light applications. Unlike conventional signs and signals which use a nominally white light source and a colored glass or plastic filter or lens to create the sign or signal, colored LEDs require no filtering. The light absorbed by the filters in the conventional products is essentially wasted, and because of this waste, the luminous efficacy of LED signs and signals is often higher than those using conventional white light sources.

Well, anyway, here’s hoping for the future.