Re: 75 lm/Watt

So it appears that for visible wavelengths (inc white light) LEDs will soon be the most efficient.

Most efficient white light sources now in production and available are many models of metal halide lamps, some of which exceed 100 lumens/watt.

As for whitish, 1KW high pressure sodium lamps get a good 140 lumens/watt.

As for visible light lamps, 180 watt SOX low pressure sodium lamps get

Keep in mind that T8 fluorescents on high frequency electronic ballasts easily get about 95, in the 80's even after ballast losses. In more optimistic situations, T5 and T8 fluorescent lamps with high frequency electronic ballasts crack a bit past 100, and get into the 90's even after ballast losses. A nominally 32 watt T8, often given upper 20's of watts by many high frequency electronic ballasts, costs maybe $2.50 each at home centers, and has rated life expectancy in typical commercial duty usage 20,000 hours or so.

- Don Klipstein ( snipped-for-privacy@misty.com)

I have yet to see ANY CCFL last as long as in incandescent.

Ever.

Their quality control is mesmerizingly awful.

You are mentioning CCFLs? Those aren't the usual compact fluorescent lamps, but cold cathode fluorescent lamps. CCFL usually refers to the miniature ones often used for LCD backlights and in scanners. The cold cathode ones don't burn out the way the hot cathode ones do, and do not have problems with frequent starting. There is even a CCFL home lighting product available at Home Depot now - at least it appears to me to be a CCFL. It is the N:Vision 3-watt candelabra base unit among the CFLs. If it dies, it would be due to breakage or from failure of the voltage boosting circuit.

As for CFLs, I have a lot of experience with them. I have experience with them in my home, homes of relatives, and in locations that I have been at frequently. I have seen some early failures concentrated into brands that I hear enough about being prone to early failures. I have seen some early failures in what appears to me to be one bad production run of a "Big 3" brand. I have seen some early failures from abuse - such as used where they will overheat, such as in recessed ceiling fixtures. And I have seen a few early failures for no good reason. But CFLs do mostly outlast "standard" incandescents by a factor of a few times.

I have seen plenty last long enough for the phosphor to noticeably degrade. That makes it easy to tell when they get replaced.

- Don Klipstein ( snipped-for-privacy@misty.com)