In m, David Nebenzahl
wrote:

Since this seems to be a fairly hot topic here I thought I'd give it
another little shove. (And I hope Don Klipstein responds, as he seems to
be one of the most knowledgeable folks here in this field.)

So it's one of the burning questions of our age: are CFLs really that
much more efficient than incandescents? Should we go whole-hog over to
what Homer Simpson calls the "twirly" light bulbs to save ourselves (by
cutting carbon emissions, etc.)?

Plus now we have a new contender, LEDs, to throw into the mix.

If I were Ayatollah of the world, here's what I think I'd do. I would
want good answers to all these questions, based on good science and not
just speculation, "common sense" or other less reliable ways of arriving
at a conclusion.

I would order a Grand Study of the problem. This study would not just
look at the efficiencies of various bulb types in isolation: it would
attempt a holistic approach, where every aspect of creating and using
light bulbs is considered, not just the simple matter of CFLs using less
electricity to emit the equivalent amount of light:

Seems to me there are the following aspects to consider:

1. Production costs:
o Energy consumed by producing each type of bulb
o Materials required by each type, and energy consumed by obtaining them
o Environmental consequences of producing each type
o Monetary cost to consumer of each type

Energy consumed for production and transportation: Thankfully, Osram
did a study, and found that to be 2% or less of the amount of energy
consumed by use during its rated life expectancy for all three types.
Osram makes incandescents, CFLs and LED "light bulbs".

http://www.ledsmagazine.com/news/6/8/4

http://www.osram-os.com/osram_os/EN/...ture_of_light/
Our_obligation/LED_life-cycle_assessment/More_Information/index.html

For the 8 watt CFL and the 8 watt LED "bulb" studied, 98-plus% of energy
consumption attributable to theior entire life cycles was energy usage to
produce light, and manufacturing, transportation and disposal account for
no more than 2%. What I see makes it appear that this is also true of the
40 watt incandescents studied.

With higher wattages, the percentage of energy used by the entire life
cycle being electricity consumed for producing light will probably be
slightly higher (more than 98%).

This study assumes 10,000 hour life for the CFL - which I consider
optimistic for real-world usage. If it lasts 2/3 of that, then 97% of
life cycle energy use is from electricity used to make light. If it lasts
half that (which I think average actual average life of CFLs now exceeds),
then 96% of life cycle energy use is from electricity consumed to produce
light.

2. Usage costs:
o Comparative energy consumption of each type per unit of light

The best LED "light bulbs" on the market have luminous efficiency about
the same as that of decent quality CFLs. This is supposed to be 5 times
that of a 230V 40W incandescent or 4 times that of 60-100W 120V
incandescents, but my experience suggests that in practice it's more like
3.33 times as good as "standard" 120V incandescents.

Longer life incandescents fare worse, with ones rated to last 3500-5000
hours usually having at most 20% of the efficiency (I think more like 24%
in practice) of good CFLs and the best LED light bulbs.

CFLs and LEDs fade more over their lives than incandescents do. CFLs
have slightly lower scotopic/photopic ratio than incandescents do. This
is why I like to figure on a CFL producing effectively about 5/6 of its
rated light output. I would do the same with LEDs despite their higher
s/p ratio, since they fade over time and I have found many of their light
output claims optimistic to some extent or another so far.

o Comparative heat produced by each type

For a given amount of power consumption, heat production is the same.

For a given amount of rated light output, incandescents produce 4 times
as much heat as good CFLs and the best LED "bulbs". But only 2.5 times
more heat materializing in the fixture - a significant part of the
incandescent's heat is infrared, materializing in the room but not in the
fixture.

(For practical purposes, including my impressions of "real world
effective useful light output", I would like to say that on average
incandescents produce 3.33 times as much heat in the room and twice as
much heat in the fixture as good CFLs and the best LED bulbs of same
practically effective light output.)

o Longevity of each type

LEDs: In a good case, 100,000 hours for colored ones, 50,000 hours for
white ones to fade to 70% of original light output. Osram rates the 8
watt LED bulb in the above study to be useful for 25,000 hours. I have
seen one white LED nightlight lose about half its output in 4,000 hours.

CFLs: Better ones now are rated for 10,000 hours, if not overheated and
with average runtime of 3 hours per start. I still see some rated 7500
hours. My experience is averaging about 60-66% of rated life in typical
home use for ones rated 6000-7500 hours.

Incandescents: The more efficient ones are either rated to last
750-1000 hours, or are halogens rated to last 2000-3000 hours. There are
longer lasting ones with life expectancy anywhere from 1500 to 20,000
hours (130V traffic signal lamp used with 120V), but efficiency decreases
as life expectancy increases.

o Comparative cost of each type, based on energy consumption and lifespan

Using 11 cents per KWH:

60 watt "standard" 870 lumen incandescent lasting 1000 hours and costing
85 cents:
$7.45 per 1,000 hours

75 watt 1100 hour 800 lumen 3-for-$1 dollar store incandescent:
$8.55 per 1,000 hours

75 watt 750 hour 1190 lumen 85-cent one dimmed to 800 lumens (65 watts,
roughly 3000 hour life expectancy):
$7.43 per 1,000 hours

75 watt 750 hour 1190 lumen 85-cent one dimmed to 870 lumens (67 watts,
roughly 2200 hour life expectancy):
$7.75 per 1,000 hours

13 watt CFL, costing $4.50, if it lasts 4500 hours, 800 lumens on a good
day:
$5.93 per 1,000 hours

18 watt CFL, costing $4.50, if it lasts 4500 hours, 1100-1200 lumens
on a good day and usually exceeding 900 for practical purposes:
$6.48 per 1,000 hours

The savings of replacing incandescents with CFLs increases as wattage of
the incandescent being replaced increases.

I am unaware of any screw-in LED light bulbs that produce 800-900
lumens.

I am aware of an LED ceiling fixture that produces good or at least
fairly good color incandescentlike warm white light, rated to produce 650
lumens from 11 watts and to usefully last 50,000 hours (Cree Lighting
LR-6). That 650 lumens is about that achieved by 60 watt reflector bulbs
and 13-15 watt CFLs with reflectors in recessed ceiling fixtures.

I somewhat remember that it is likely to be improved in efficiency in
the near future - maybe to about 800-900 lumens with 11 or 12 watt power
consumption.

I do not know how much these cost and they require installation.

3. Disposal costs:
o Actual physical disposal (recycling, landfilling) costs

I somewhat remember landfilling costing Philaelphia around $70/ton
around 1990 or earlier in the 1990's - could be more like $100/ton now.
Plus maybe a few dollars per ton to transport trash to the landfill.

If you take your dead CFLs with you to Home Depot next time you go
there, proper recycling does not cost you anything. I hope the actual
cost is included in the price Home Depot charges for their CFLs.

o Environmental consequences of disposing of each type

The main concern is that landfilled CFLs would release about 3.5-4
milligrams of mercury. On average, ones replacing 60 watt or higher
incandescents in the USA save the environment from at least that much by
reducing coal burning.

I think these "top-level" categories should cover most of the important
questions that should be answered in order to set light-bulb usage policies.

One of the most important things to consider, I think, is the fact that
CFLs contain fairly complex electronics, requiring construction at the
front end and disposal at the back end. How much energy does this all
consume? (That little matter of mercury in CFLs also demands investigation.)

It's important to look at something like this holistically so that we
don't end up embracing a policy that, to use an analogy, yields a barrel
of oil while requiring two barrels of oil to produce it.

I think I answered most of the questions here, though not all. If I see
a followup asking for more, I will try to get to it later this week.

- Don Klipstein )