I know there are a lot of variables but could someone point me to ball park figures for various lighting technologies?
For example manufacturers (optimistically?) claim an 11W flourescent lamp produces about the same amount of light as a 60W incandescent.
What about LED lamps that are now becoming available? How do they compare? Would a 4.5W output LED be bright enough for use as a ceiling mounted downlighter in a kitchen etc
Anyone know of some good sources for LED based lamps for use in buildings?
Look at and compare the lumen output of the various devices. The lumen output rating should be printed on both the fluorescent and the incandescent bulbs. That way, you're comparing apples to apples.
-- Dave M MasonDG44 at comcast dot net (Just subsitute the appropriate characters in the address)
Never take a laxative and a sleeping pill at the same time!!
He should've thoroughly read Don Klipstein's Lighting FAQ and ancillary documents, LEDs, Compact Fluos, etc. before asking here. He would not have had to ask here at all, then.
Roughly, roughly, a compact fluorescent lamp produces as much light as an incandescent lamp of 3-4 times as much wattage. Good compact fluorescents normally produce 4 times as much light as good incandescents, except compact fluorescents can be dimmed by non-ideal temperatures, heat buildup in fixtures, etc. Another thing - if you put a compact fluorescent in a fixture designed for an incandescent, the light may not be distributed in a less favorable manner than that of the incandescent.
Please check out my compact fluorescent stuff at:
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"Standard" fluorescents of the more usual "shades of white", especially the 4 foot T8 (1 inch diameter) ones, are a little more efficient than compact fluorescents.
One more thing: Fluorescent lamps and incandescent lamps can vary significantly in efficiency with manufacturer and model due to various issues of design and quality.
For example, in the USA a "standard" 100 watt incandescent lamp by one of the "Big Three" makers produces 1710 lumens, sometimes claimed as high as 1730 or 1750. I see off-brand 100 watt incandescents in packages claiming as low as 1100 lumens, claimed life expectancy not exceeding that of longer-life "Big Three" 100W lamps claimed over 1600 lumens, and I don't only see such junkers in dollar stores.
Compact fluorescents with magnetic ballasts are usually less efficient than ones with electronic ballasts and they also have quality issues.
Non-compact fluorescents also suffer from ballast issues. Also, ones with color rendering index higher than 86 or so have less photometric output than most usual ones with rated color rendering index in the range of 53 to 86.
The best available white LEDs have typical overall luminous efficacy around 1.5 to 2 times that of most home-illumination-purpose incandescents, assuming you have no losses in any ballast/driver circuitry.
There are some problems:
LEDs are extremely expensive for their light output. 5 watt LEDs cost quite a few $$. I just checked out Quickar Electronics, which is a place to get just one or a few, and I just saw a price for a 5 watt white one at about . Time for that to be paid back by electricity savings over a 15 watt incandescent, assuming electricity cost of 10 cents per KWH (roughly the USA national average): 30,000 operating hours. Don't forget the cost of the ballast or driver circuitry even if you can get a better price on the LED.
1a. White LEDs do not last forever. Higher figures that I do not know to be dishonest or wrong for claimed life expectancy are 50,000 hours. It is easy to get a fraction of that. The main problem is that the usual white LEDs have a phosphor that wears out during use. This will exacerbate the economic disadvantage of using LEDs of late 2004 state-of-the-art over more usual light sources for home lighting.
As Vic Roberts (someone else who you may run into when the subject is illumination with LEDs) likes to point out, LEDs have another issue: They vary considerably in light output from one piece to another, even of the same part number. They also vary a little in voltage drop at a given current, often and maybe usually without much positive correlation in light output at a given current. The best minimum guaranteed overall luminous efficacy for a higher power white LED that I have heard of so far is about 16.6 lumens per watt, which is just a little higher than that of most but not all common incandescents. And this requires a rather optimistic thermal assumption of a heatsink being at 25 degrees C and no losses in the ballast/driver circuit.
LEDs do have their place already in more specialized lighting applications such as flashlights and traffic signals. To see how LEDs get ahead in those applications, please check out this page of mine:
Thanks for the info. I was hoping they might be good enough to replace low end Halogen downlights but it seems unlikely.
The UK building regs require a certain number of low energy lamps (>40 Lumins per Watt) to be fitted in a new house. CFL downlights exist but small diameter models are too tall to fit in my ceiling void. The best I've found fit in a 100mm void but are 160mm diameter overall with a 120mm light aperture. They look slightly too large.
Cost aside it occured to me that LED's might offer a solution because they are physically small and can be dimmed easily. Their small size might also help with sound and fire regs compliance (no need to cut away insulation.
...so it seems they wouldn't meet the energy efficiency regs yet.
I believe Halide lamps might produce more than 40L/W but I've not done enough research yet. I read somewhere that they take a long time to warm up and I don't know if they can be dimmed.
I have an industrial application where we used compact flourescents. The magnetic ballasts actually had a much better life expectancy than the electronic version.
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