I used to like
fluorescent lights and then I changed my mind.
As the years
passed, I found more and more folks like me, and more and more reasons
to be uncomfortable with fluorescent lights. When some people see
that I don't use them, they try to tell me about how great they
are. When I try to explain why I prefer incandescent, I nearly always
get a dismissive wave signaling that I am clearly a fool
and whatever tripe I am about to utter is clearly not worth their
time. This article represents a glimpse into that tripe.
If you leave
all of the lightbulbs in your house on 24/7, then replacing all
of the incandescent light bulbs in your house with CFL light bulbs
will save you money. For people that typically leave lights off
when not in use, it turns out that incandescent light is cheaper
than fluorescent light the exact opposite of what we have
been told all these years.
With a little
knowledge, you can stop wasting money on CFLs. Both in the short
term and the long term. The long term stuff includes tax issues
and the toxicity tie-in which leads to superfund cleanups and medical
a fluorescent light bulb will last ten times longer than an incandescent.
It says so right on the box. When my CFL bulbs seemed to burn out
faster than my incandescent bulbs, I thought I was doing something
wrong or I had bad batch of bulbs. Most of the people I visited
with about CFLs reported that they were experiencing something similar.
So I started to do more research.
Here is a "100
watt long life incandescent light bulb" on amazon for $1.52.
It says that it has a lifespan of 25,000 hours. Apparently, a standard
bulb has a lifespan of 1000 hours. Here is a "100
watt equivalent CFL" on amazon for $2.87. It claims a lifespan
of 8,000 hours. I searched for "CFL 100" and came up with bulbs
claiming a lifespan of 6,000 to 10,000 hours. The claim of 8,000
hours seemed the most common.
light bulbs don't do well when they are turned on and off a lot.
While this is true of incandescent bulbs as well, fluorescent bulbs
are far more sensitive this way. Wikipedia says "In the case of
a 5-minute on/off cycle the lifespan of a CFL can be reduced to
'close to that of incandescent light bulbs'." Most household light
bulb use is less than five minutes: a trip to the bathroom; looking
in a closet; a snack from the kitchen; find something in the bedroom;
etc. Optimal use for a fluorescent light is to be left on all the
time at temperatures between 50 and 80 degrees (F). You can still
experience savings when an area needs to be illuminated by artificial
light for ten hours or more at a time. But for most households,
the need is for a few lights to be on for an hour in the morning
and two to five hours at night, and most lights to be on for one
to ten minutes as needed. If you try to leave the light on longer
so the bulb will last longer, the electricity savings are then lost.
A more accurate longevity statement would be "250 to 10,000 hours
depending on use."
for 504 hours of time that the lights had power although
they probably burned out before the 504 hour mark. The incandescent
and both of the fluorescents were dead at the end of six weeks.
I suspect that the 1000 hour rated incandescent outlasted the 10,000
hour rated fluorescent but they don't say. The important
lesson here is that the fluorescent light bulb failed before reaching
5.1% of its rated lifespan (and, yes, the incandescent failed before
reaching 51% of its rated lifespan).
A friend of mine told me about how boats long ago used incandescent
bulbs that were re-usable. The bulbs all had a way of opening
them up and replacing the filament. And the boats carried a light
bulb repair kit, complete with a bunch of filaments. Imagine: a
light bulb that lasts forever. You just have to mend it with a bit
of filament every couple of years. Maybe filaments come in 100 packs
manufacturers exaggerate brightness
CFL article used a light meter to measure the light coming from
four different 60 watt incandescent bulbs and five different fluorescent
bulbs claiming to have light equivalent to a 60 watt bulb. The result
was that the average incandescent bulb was 64.5% brighter. And the
results were shockingly consistent.
decrease in lumens over time
lights put out less light over time. I remember when I used to use
fluorescent bulbs, when I replaced a bulb of the same power, the
new bulb seemed about twice as bright as the old bulb. But when
I replace an incandescent bulb, they seem about the same level of
bright. Is it possible that all of the money saving claims of the
CFL producing four times more light per watt is based on a brand
new bulb? Maybe they should say that it produces the same light
as a 60 watt incandescent bulb in the beginning and a 30 watt incandescent
bulb at the end. It turns out that my instincts were not too far
off. From wikipedia: "CFLs produce less light later in their lives
than when they are new. The light output decay is exponential, with
the fastest losses being soon after the lamp is first used. By the
end of their lives, CFLs can be expected to produce 70-80% of their
original light output."
net CFL light
per watt correction
At this point
I need to combine the light per watt information we have so far.
To do this, I want to imagine a room (A) with 100 incandescent lightbulbs,
and another room (B) with 100 CFLs. The goal is to figure out how
many more CFL lightbulbs we need to add to B have the same average
light as A. Which is what is advertised on the CFL box.
the exaggeration, we have to add 64.5 bulbs. So we now have 164.5.
Next we have
the issue of the bulbs giving off less light as time passes. So
if the light starts at 100%, quickly degrades to 80% and then slowly
ends up 75%, then a rough average approximation of that is 80%.
It's as if I put in five light bulbs and one does not work. To go
from four working lights to five, I need to add one. From the perspective
of the four bulbs, I need a 25% increase. 25% of 164.5 is 41.125.
This brings us to a total of 205.625.
To get the
brightness claimed by the CFL manufacturer, we need more than twice
as many CFLs. I'm going to use the number 105.6 and call this "the
CFL brightness adjustment".
There are claims
that a CFL gives off three to five times more light per watt than
incandescent. A 10 watt CFL claims to put out the same amount of
light as 40 watt incandescent bulb. Four times more light. When
we factor in "the CFL brightness adjustment", we need 1.056 more
light bulbs. In the end, this means that the CFL is 1.95 times as
bright as the incandescent. This is the number I am going to use
for the rest of this article as the actual light per watt improvement.
poorly for first two minutes
First, a fluorescent
light uses about 20 times more power in the first second to get
started. So, for a two minute cycle, the total power consumed is
16% higher. Then it can take one to three minutes to reach full
brightness. At first, the light might be giving off only 30% of
it's maximum light. So if you are only using the light for a minute
or two, the efficiency of light per watt is worse than incandescent.
If the light is in a place where you never have the lights on more
than a minute or two, CFLs are far more expensive than incandescent.
Both for the cost of the bulb and for the cost of the electricity.
mythbusters thing and the wikipedia article, I think it is fair
to say that if 100% of the use of a CFL is a series of two minute
jobs, the overall lifespan of the bulb is closer to 500 hours. Probably
seems the most common. So if we assume 30% at time zero, and 80%
at two minutes, that makes for an average of 55%. When you work
in the extra power, this makes the two minute scenario roughly double
poorly in the cold
lights don't work in the cold. Some fluorescent lights have been
modified with special ballasts to tolerate temperatures below freezing,
but they will still fail when it gets to, say, zero (F), although
I have heard of some that will go a little colder.
bulbs are toxic
light bulb contains toxins. Primarily mercury. The toxin issue is
severe enough that you are not supposed to throw them away when
they die. You are supposed to dispose of them in an appropriate
facility. I guess people are supposed to drive their light bulb
to the facility for proper disposal? I would call that an extra
expense for CFL your time has value and the fuel to drive
there costs something (tiny CFL funeral arrangements are optional).
How many people know that fluorescent bulbs are not to be thrown
in the garbage? I suspect that 99% of dead fluorescent light bulbs
get thrown in the garbage and their toxins can do their toxic thing.
When a CFL
breaks in your home, that toxin is now in your home. Do NOT touch
the mercury! Cleanup and proper disposal is far too complicated
to go into in this article. Here
is a stressful story.
A case has
been made about the toxicity where if you figure in the amount of
energy saved by a fluorescent light bulb, and you work in the average
amount of power that comes from coal, and the amount of mercury
that is in coal, then if you assume that a fluorescent bulb lasts
10,000 hours, then there is less mercury overall with the fluorescent
Put a different
assume 8000 hours of light. The incandescent will be responsible
for 5.8 mg of mercury pollution from coal plants, and zero from
the bulb. The fluorescent will be responsible for 1.2 mg from the
coal plants and 0.6 mg in the bulb.
I have two
concerns with this:
A CFL has three to five milligrams of mercury per bulb. The report
elected to count only 0.6 mg because that is what they estimate
would leak out of landfills. Therefore, the rest is trapped in
the landfill and they are okay with that. I'm not. Next, there
is the lifespan of the bulb. 8,000 hours is reasonable for a light
that is left on 24/7. For lights in a typical home, 1,000 hours
is more accurate. Their report shows the incandescent uses 5.8
mg from the power plants and the fluorescent uses 1.2. So the
incandescent uses 4.8 times more power? Further, the report is
trying to convey pollution per lumens, so this calls for "the
CFL brightness adjustment". My math says 16.4 CFL bulbs with 4
mg each of mercury plus 3.0 mg of pollution from coal. That makes
CFL come in at about 68.6 mg of mercury pollution. 11.8 times
dirtier than incandescent. And that's just for mercury toxicity
there may be other toxins in CFLs.
Instead of justifying toxic light bulbs with information about
how toxic power generation is, I propose we use the non-toxic
light bulbs and work on cleaning up our pollution generating power
plants. Until the power plants are cleaned up, we can focus on
other ways of saving electricity that are far more effective (later
in this article).