Happy solstice! How better to observe than lots of light, but little juice. Earlier I had written on nulling out the electricity of my vehicle, by saving it elsewhere- “negawatts.” I said nothing on LEDs (solid state emitters) at the time. While efficient, very long-lived, and fast, they were almost fifty bucks. Then 40, then 30… see where I’m going?
This Spring, Cree’s bombshell hit shelves: dimmable LEDs, in the usual A19 thread (“Edison base”), at ten dollars (40W equivalent; a “60W” was $14.) At 6 actual Watts, I’d score 34 negawatts in one move. Still, I held out. Only one store (Home Depot) had it, only in multi-packs. But reviews have been kind, they’re now sold individually, and the price has fallen (after rebates) to… six bucks. It’s now a no-brainer: more efficient than compact fluorescents (barely), with no hum/flicker, lag time, or power-cycling issues, at nearly the same price. If it all works, that is. Does it?
I didn’t need dimming, so that box is checked. The cheap one is “warm white” (2700K- faintly red like an incandescent), which is fine for many domestic purposes, or at least mine. The claimed life is decades– way too long to actually test myself.
That’s the brilliant part, though (literally and figuratively). At six dollars, this light doesn’t actually have to last decades- I’m ahead anyway. The math works out like this: my house was full of the last owner’s incandescents. Replacing one of them with this Cree saves 34 Watts. The national average rate for electricity is 12 cents per kilowatt-hour. A six-dollar LED must then score five nega-dollars to beat an incandescent in total cost of ownership (TCO). At 12¢, that would take a bulb life of just 1226 hours. That’s 409 calendar days at a duty cycle of three hours per day (i.e., domestic use), or anywhere from 154 to just 123 days in an office or factory. No biggie.
In effect, this bulb would have to fall short of its design life by an order of magnitude to not pay off. Meanwhile, the warranty is ten years- as long as you save your receipt, this bulb will pay off, at least in terms of your dollars.
Of course, if you’re replacing a compact fluorescent, not an incandescent, the energy savings are lower, and the payback time is longer. But compact fluorescents tend to die in strange ways, especially in applications like hallways or bathrooms that cycle frequently. They also tend to buzz or flicker, and many don’t work with dimmers. LEDs still make sense in hallways, basements and storage rooms, etc. I’m saving my receipt in any case. I’m also not counting the savings in air conditioning, since every Watt that doesn’t turn into photons turns into heat instead. Incandescents have a terrible photon efficiency, and many of those photons are in the infrared (heat) where humans can’t even see. All told, ~97% of the Watts going into an incandescent get wasted.
Nor am I counting the embodied energy in the materials. This LED seems to have more metal than an incandescent, but less glass, which embodies more energy. It definitely has way less glass than a compact fluorescent. In any case, the lifetime of decades, versus an incandescent, means a lifetime materials savings (such as factory tooling, handling and shipping, packaging, etc.), even without the savings in electricity consumption.
But does it work? Well enough- this light lights, of course. One complaint of LEDs as a category is their varying color renditions. Incandescents produce broad-spectrum light, mostly yellowish but including reds, greens and blues across the range (plus infrared). Meanwhile, a “dumb” (bare) LED die emits monochromatic light. To get “white,” you either combine red, green, and blue LEDs, or use phosphors like a fluorescent. Phosphors absorb one color, then re-emit it as other colors. The choice of phosphors versus the choice of die sets the “whiteness.”
Again, this Cree model works fine in my boring home. I don’t do any catalog or magazine shots, colorimetry work, or anything else that needs precision colors or accurate white balance. I don’t even wear flashy clothes. I might get the opinion of a friend who does makeup professionally, but that would be a bit pedantic versus my domestic needs (and probably yours). This warm white model is definitely warm, but that’s like an incandescent, which people appear to like, and not like daylight itself or more-accurate bulbs. The “60W” comes in both 2700K and 5000K (“cool white”) versions. Cree is now selling a TW (True White) model, if you actually care enough to spend a few bucks more.
The unit gets warm to the touch, of course, but never enough to recoil your hand. This is significant, because LEDs are fried by extreme temperatures. Previous attempts at domestic LEDs had giant heat sinks for this reason. Somehow, Cree got the fins down, while still being confident enough to offer a 10-year warranty.
Maybe a bigger issue is a “cold spot”- or maybe not. Based on the arrangement of the twenty individual dies (which you can see in this teardown), light is emitted in a band, not down the axis of the unit- “broadside,” instead of “endfire.” The envelope thus appears to have a dead spot- or does it? The glass housing bends light, and a rubber layer (that’s not frosted glass) scatters it. I attempted to photograph the spot on the unit itself, but couldn’t capture it with any reasonable settings.
There doesn’t appear to be a shadow on the walls opposite the cold spot. I held up a large white reflector, and no dim spot is visible to my eye. I circled around the light fixture just to be sure. Finally I busted out the light meter; the eye and brain can gloss over a surprising amount. Any dim spot appears to be within the readout accuracy of the meter I used. Looks like the amount of light bouncing around the glass and “rubber” effectively compensates for the broadside die layout. And that’s before any scattering off light fixtures, lampshades, walls, etc.
Still, I wouldn’t recommend this particular LED product for a reading lamp or task lamp. There are “endfire” (directional) LED products specifically for that, including ones I already use for task lighting. Flashlights, for this reason, are dominated by LEDs now.
Not an issue at all? Shape and housings. The industry has learned to produce “normal” (incandescent) shapes, either for tight fixtures, shades, and enclosures, or simply for those consumers weirded out by anything that looks different. Cree does recommend against putting this product in certain fixtures that get hot, due to the dies getting fried. This includes putting LEDs next to incandescents.
I suppose the only other result I can report (other than busting out a spectrometer) is the lifetime of my particular unit. I don’t intend to be blogging decades from now, but I’ll certainly pipe up if this thing should blow before ~1226 hours. Cree is a major name in the LED world, so they seem to be doing something right.
Either way, LEDs look to be here to stay, in some form or other. Philips is not sitting by; they already had a low-cost lamp, just not ten bucks. They, too, had figured out how to get the heat sink down, and their LED lamp doesn’t appear to have a typical heat sink at first glance. Philips has stated openly that they will challenge Cree; one financial analyst has stated that 2014 will be the Year Of The LED. A child born today may not learn how to change a “light bulb” until they move into their own household… in the 2030s.