I last looked a few months ago. They were still expensive, still dim, and still not as efficient as compact fluorescent.

Yes, I said not as efficient as CF. Despite all the noise about LEDs being so efficient, that really applies only when you need just a little light (because low output in anything else is woefully inefficient), or when you need light in the primary colors.

White LEDs are making good progress in the lab, but they have a considerable way to go before you can buy ones that even match compact fluorescent in efficiency. Linear fluorescent is even farther ahead. Many of the LED can fixtures commercially available don't meet California Title 24 standards, and the ones that do just barely scrape by.

Bottom line is that LEDs are great for night lights, indicators, traffic lights, etc. They haven't yet arrived for area lighting. They may eventually be a player for home lighting, but I'm thinking closer to 10 years from now than to 2.

This Old House recently featured some LED lighting in the Green house project in Austin, but I have not been able to find out anything about it. All my research backs what davidr said. So far, anyway.

LED lighting does not yet qualify as high-efficacy, which is what is needed to comply with California's Title 24 requirements for energy efficient lighting. LED uses very little power, but also emits very little light. It may come in less than 10 years, but as far as I can tell, it isn't here yet.

So have you actually gotten some of these LED lights and used them? They still seem really expensive so far but I'd like to try a couple of them just to see. Our house is a stand alone photovoltaic house so energy efficiency is extremely important to us.

So have you actually gotten some of these LED lights and used them?

No, I didn't buy any. I looked at the specs for power consumption and lumen output, and wasn't impressed.

A lot of the vendors, especially the guys on Ebay, sort of downplay the actual lumen output. Or they'll try to claim that 300 lumens is "equivalent to a 40 watt incandescent," when it's really more like about a 30 watt incandescent. Some of the CF manufacturers also did this 10-15 years ago and got a bad name as a result.

If energy efficiency is crucial to you, I recommend linear fluorescents with high power factor electronic ballasts. Choose the lamps by efficacy (lumen output for a given Wattage). Cool (high color temperature) lamps usually have somewhat higher efficacy than the warmer colors. To minimize ballast losses, use fewer fixtures, but make them higher wattage ones. One 32 Watt fixture will usually be more efficient than two 15 Watt fixtures.

I've installed some LED rope lights, using the multi-color strings (red, blue, yellow, green). They give off a very soft peach-colored light overall that is nice for some applications. I just put a string inside some cove molding in a dining room tray ceiling. Quite nice, but even with about 100 watts total, it seems barely enough to eat by.

I found this on the This Old House website in an article by lighting designer Mark Loeffler on efficient lighting for TOH's Austin project: "Looking a little into the future, LED (light emitting diodes) lighting is something to watch. Although much more expensive right now than other light sources, this solid-state technology is notable for its ability to produce attractive white light at about 100 lumens per watt lasting 50,000 hours or more. Researchers predict that within the next few years, affordable consumer-grade 'white' lighting products will approach 200 lumens per watt efficacy."

My guess is that 100 lumens per watt LED bulb is still in the laboratory, and likely costs a mint. The ones I've seen on the market are nowhere near that bright. I really hope he's right about the "few years" prediction, but I'm not going to hold my breath.

My guess is that 100 lumens per watt LED bulb is still in the laboratory, and likely costs a mint.

Exactly. I would also point out that a $5 LED with an efficacy of 150 lumens per watt isn't very practical for home lighting when its output is only 50 or 100 lumens. A 75 watt incandescent lamp produces about 1200 lumens. Think about how many 75 watt incandescent lamps the usual kitchen fitted with can lights requires, and add up the total cost for LEDs. Ouch. And before you dismiss this, consider that blue LEDs cost about that much per copy, 10 or so years ago.

On the other hand, as I said above, LEDs really shine (groan) in low-output applications, where incandescent lamps and even fluorescents have poor efficacy.

My point is that we have to consider what technology is appropriate for a given application. It's important to distinguish brightness and illumination. You need brightness when you want a light TO BE SEEN. You need illumination when you want to SEE BY a light.

LEDs have high brightness but poor illumination qualities (low lumen output). Because of the brightness, it can actually be painful to look at an LED. This makes them appropriate technology for situations where the light source must be seen at a distance. They're good for indicators such as automotive taillights and traffic signals.

Because they emit light from a very small area, LEDs aren't very good for lighting up rooms. However, because incandescents and even fluorescents diminish markedly in efficiency as they're asked to produce lower illumination (lumen output), LEDs can be an acceptable alternative. (But find a way to eliminate ballast losses, and fluorescents could still win at this game.)

Fluorescents have high illumination (lumen output) but low brightness. They produce a smooth, even light. It is not usually painful to look at a fluorescent, because it emits light from a large area. This makes them appropriate for lighting up rooms, but not so good as indicators.

Rather than follow up on this any further here, I would direct you to Don Klipstein's outstanding lighting pages. Don follows lighting developments, especially in LEDs, pretty closely. This page has more on why LEDs are so well suited to flashlights and traffic signals. Anyone with an interest in lighting, especially high efficacy lighting, will most likely find Don's pages very interesting.

A huge hidden dangers that most Chinese companies do not have the LED current core technologies, such as, LED chip technology is mainly controlled by Cree, Philips , Osram, Nichia and a few foreign hands.

Here is a link that might be useful: 90W led grow lights