I will only point out a couple of things. First all else being equal
halogen is slightly more efficient, but not a lot. All else is never equal.
Most halogen lamps are designed to last longer, that good, but it also
means they loose some efficiency.
Many halogen lamps make better use of the light they make (those with
reflectors) so the total output is no more, but you get more light where you
I like the long life and the color of the light.
In theory, an incandescent bulb should be about as efficient as an
equivalent halogen bulb. But all is not equivalent. Most incandescents
produce omnidirectional lighting, while virtually all halogens are
directional and have well-designed reflectors to ensure that most of their
output is not wasted.
In this case, the lumens per watt rating is deceiving since it is a measure
of the bulb's total light output, not its intensity of light in the
direction you need.. A directional halogen will definitely produce much
brighter light at the same wattage as an ordinary incandescent.
Hallogens are a lot smaller and therefore tend to have more attractive,
trendy fixtures. They also produce whiter light.
I might add one other difference. Because halogens generally have more
compact filaments and they are encased in a smaller area (both part of the
halogen cycle that gives them the longer life) the result is a little more
visible light and less infrared (heat).
Some may realized that halogens get hotter and expect that they give off
less heat, but while they are hotter they have less surface area and the net
heat loss is less.
As you pointed out that there are so many other factors, that it is hard
to point out any one.
Another point, not directly related to halogens, are dimmers. While a
dimmer will save energy ,when used, using a larger bulb, of the same design,
and them dimming it to get the same light will use more energy. Long life
bulbs also use more energy per light output for the same reason. The
original writer had the right idea of comparing light output to watts but
missed many other factors.
Usually, a halogen lasts about 3 times as long as "standard"
incandescents. And Sylvania appears better than Philips, according to
numbers that I see on some of their packages and an article that I saw in
Consumer Reports, I believe in October 1992. Philips "Halogena" hardly
to not at all outshines plain incandescents, while Sylvania "Capsylite" of
usual wattages (as opposed to oddball wattages) outsines plain
incandescents by 5% or more. Compared to longer life incandescents with
life expectancy similar to that of halogens, halogens usually produce
10-20% more light.
Halogens produce a slightly whiter light than regular incandescents,
especially the longer life ones, do.
Then again, compact fluorescents typically consume about 30% of the
electricity of incandescents of the same light output, and they usually
outlast halogens - often by a factor of 2, sometimes 3.
Compact fluorescents do not work well everywhere. Only some are good
outdoors, only some are good in small enclosed fixtures and recessed
ceiling fixtures, and life is compromised if they are used where they do
not stay on for long when they are turned on. See:
http://www.misty.com/~don/cf.html (General info, mostly by Sam G.)
http://www.misty.com/~don/cfbest.html (mostly brand/model-specific data)
- Don Klipstein ( firstname.lastname@example.org, http://www.misty.com/~don/index.html )
Lumen rating is for a new bulb. In a standard incandescent bulb, as the
from the filament, it is deposited on the inside wall of the glass bulb,
reducing the light
output of the bulb. In a halogen bulb, the tungsten is deposited back on the
the bulb's light output stays fairly constant over it's lifetime (that's also
the reason for
it's longer life).
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