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Compact fluorescent light bulbs (CFL's)

[an error occurred while processing this directive]CFLs aren't your only option for slashing your lighting costs these days.  LED bulbs are better for most purposes, and they're finally cheap enough, too.  See my page on LEDs vs. CFLs for the details.  The rest of this page will look at just CFLs, in more detail.

Here's are the benefits of CFL's:

  • Use 75% less energy than regular light bulbs.
  • Last about 10 times as long as regular light bulbs.
  • Produce similar quality light as regular light bulbs (nothing like old-style fluorescents).
  • Cost as little as $1.50.
  • Don't generate ridiculous amounts of heat (which you would have to pay to remove with AC).

And here are the downsides:

  • Most of them can't be used with dimmer switches. (Some can; check the package.)
  • Cheap ones burn out really quickly. (Buy Energy Star-rated bulbs, or bulbs with a warranty.)
  • Most start dim and take a minute or two to reach full brightness.
  • They contain a tiny amount of mercury, which might be an issue if you break a bulb and you're careless about how you clean it up.  (More on this in a minute.)
  • If you use an illuminated wall switch to control them, they might burn out faster.
  • They produce a higher electromagnetic field than regular bulbs, and there is controversy about whether this has health effects.  (More on this in a minute, too.)

You start saving with CFLs as soon as you screw them in.  Here's a calculator that shows you how much.  (If you want to see a calculator comparing standard, CFL, and LED, just click the link.)

Compact Fluorescent Savings Calculator
Your lights

Number of bulbs

Wattage (original)

Hours on per day

Cost of electricity

Your Savings

10 years

Cost with old bulbs:


Cost with CFL's:




And that's just the electricity savings.  Since a good CFL lasts 10 times longer than an old-style bulb, that's a lot fewer bulbs to buy.  This is especially important for large commercial applications, where the cost of labor to constantly replace old-style bulbs can be significant.

You'll save even more in summer months, because CFL's run cooler than old-style bulbs, so you'll spend less money to cool your home or office. 

To figure your electricity savings manually, ignoring heating/cooling issues, use this formula:

Watts  x  Hours Used

   x  Cost per kilowatt-hour = Total Cost


For example, let's say you replace ten 60-watt bulbs with ten 15-watt CFL bulbs. That saves you 45 watts per bulb, or 450 watts for all ten. Let's say all your lights were on for six hours a day, five days a week. That's thirty hours a week, or about 1500 hours a year. So your 450 watts savings times 1500 hours a year = 675,00 watt-hours. Divide by 1000 and you have 675 kilowatt-hours (kWh).  If you're paying 16 per kilowatt-hour, then you'll save $108 a year.

Modern CFL's produce great light.  If you saw the old ones and didn't like the kind of light they put out, you're in for a surprise.  Here's what Popular Mechanics said:

The results surprised us.... [H]ere was the real shocker: When it came to the overall quality of the light, all the CFLs scored higher than our incandescent control bulb.  In other words, the new fluorescent bulbs aren't just better for both your wallet and the environment, they produce better light.


How to buy CFL's

When you buy CFL bulbs the package will be labeled to show you how many watts it's equivalent to.  For example, a 15-watt CFL bulb package will say something like "60 watt equivalent". They have to say that otherwise people would look at the package and think, "15 watts? That's not nearly enough light!" But it is, because a 15-watt CFL bulb puts out as much light as a standard 60-watt bulb.

Although CFL's generally last for years longer than regular bulbs, the cheap kind can burn out quickly.  I therefore recommend buying only Energy Star-rated CFL's, or at least ones that come with a 5+ year warranty.  If the package says "lasts five years" that's not good enough, you want a 5+ year guarantee.

Make sure to get a color temperature you'll be happy with.  The light bulbs you're replacing are probably "warm", around 2800k.  Anything above ~3500k will have a bluish tint to it, and the higher the blue, the "colder" (more blue) it gets.  If you want similar light to what you probably have now, go for "warm" CFL's, less than 3500k, the lower the better.

CFLs come in dimmable and 3-way-switch flavors, if you want those varieties.  A regular, non-3-way CFL can be used in a 3-way socket (just like any other non-3-way bulb), it'll just produce the same amount of light as it would in a regular socket.  And when you turn the knob, two positions will be "on" (maximum brightness) and two will be "off".

If you're in a super-cold environment, note that most CFL's run dim in very cold temperatures, and most won't run at all below 20F.  (Paralite makes some they claim will work down to minus 20F.)  If you're using them outside as floodlights, then make sure you get the kind that are labeled for cold-weather use.  One reader notes that he put a $10 bug light sleeve around the light which acted like insulation, and kept the light just warm enough that it would work.


CFL longevity

It's no secret:  the cheaper CFL's often burn out quickly.  Sometimes even a batch of name-brand bulbs can be bad.  I strongly recommend you buy only CFLs with the Energy Star seal or that come with a warranty.  Energy Star bulbs have to meet strict specs for lifespan, and they have to maintain 80% of the initial light output at 40% of their rated lifetime. (Energy Star)

It's a myth that frequent cycling (turning lights and on off) greatly reduces CFL life.  When CFLs fail, it's generally because they were cheap and poorly made, not because they were turned on and off too much. In Consumer Reports' rigorous testing, after 3000 hours with frequent on-off cycling, most of their CFL's are still going strong, and the Energy Star bulbs are lasting longer than the non-ES bulbs.  (CR article, subscription required)  And to get the Energy Star label, 5 of 6 test bulbs have to stay alive after being cycled for half the number of stated life-hours.  For example, a bulb with a claimed life of 6000 hours is turned on for 5 minutes and off for 5 minutes, a total of 3000 times. (Energy Star, PDF) 

It's never better to leave the lights on

It's never better to leave the lights on when you leave a room.  It's always better to turn them off.  It doesn't take more electricity to turn them back on, contrary to some stupid myth.  There is no surge when you turn on a CFL (or anything else in your house), in practical terms.  "In practical terms" means any surge that happens is so tiny it can't even easily be measured.  You're certainly not paying for it, because it's too microscopic to show up on your electric bill.

If a CFL used twice as much energy as normal for the first full second it was on, then that would mean you're paying for one extra second of electricity.  You'd have to flip the light on close to 10,000 times before you'd pay even one penny in electrical costs.

Mythbusters did a story on this and confirmed what I'm saying.  They concluded that it would pay to keep a CFL light on only if you're leaving the room for 1/66th of a second or less.

CFL's and illuminated light switches

Light switches that light up when the main light is off can cause problems with CFLs.  Illuminated light switches work by passing some of the current through the switch to light it up when the switch is off, and that tiny amount of current also passes through to the bulb.  With an old-school incandescent bulb there's no problem, because there's not enough current for the bulb to fire.  But some CFLs are sensitive to even small amounts of current, and can flicker when the switch is off.  Besides being annoying, this can also potentially burn out the CFL bulbs faster.  Solution:  Either use regular (non-illuminated) wall switches, or use LED light bulbs.  (More from Will Nicholes.  Also worth noting is that a master electrician thinks that CFL flicker on a lighted switch is abnormal and that any CFL flicker means there's actually a wiring problem.)

The great mercury scare

Let me debunk this the easy way:  The median mercury exposure from breaking a CFL is only 0.07 mcg, while single serving of Albacore tuna has 48 mcg.  The tuna has seven hundred times as much! (Illuminating Engineering Society, 2009)  The amount of mercury exposure by breaking a CFL is just not that significant.  As Popular Mechanics put it:

Each bulb contains an average of 5 milligrams of mercury, "which is just enough to cover a ballpoint pen tip," says Leslie, associate director of the Lighting Research Center at Rensselaer [Polytechnic Institute]. "Though it's nothing to laugh at, unless you wipe up mercury [without gloves] and then lick your hand, you're probably going to be okay.

And actually, Consumer Reports says CFL's have even less mercury than is commonly reported.  According to their tests, all the bulbs had a lot less than 5 mg, and some had less than 1 mg. (CR article, subscription required)

And while the risk from a broken CFL is tiny, the risk from a bulb that never breaks is zero. You'd think that would be obvious, but some of the hysteria surrounding CFL's is coming from pages that say that just having CFL's installed in your home is "killing you slowly"?which is absolute nonsense.

If a bulb does break, you just take some simple steps to minimize your exposure when cleaning it up.  You certainly don't have to call in a hazmat team.  One woman got bad advice that she needed to do just that, and the anti-CFL folks have been having a field day with that one, not admitting that the advice this person received about employing a hazmat team was simply wrong.

Those who are still concerned can just use a bulb with a plastic cover.  Check out the picture at right of a bulb I bought recently.  It's really unlikely that one of these bulbs will break in the first place, but if it does, it's sealed.  Problem solved.

Another idea being bandied about is that the use of CFL's is resulting in a lot more mercury getting into the environment, in general.  Not true, because power plants put out tons of mercury. They put out more mercury to power the bulb, than is contained in the bulb. (Ohio EPA)   In fact, for each bulb you don't replace with a CFL, you're putting ten mg. of mercury straight into the air. (Popular MechanicsUsing CFL's dramatically reduces mercury emissions at the power plant.

And mercury at the power plant is worse than mercury in lightbulbs, because power plant mercury goes straight into the air where it's impossible to recycle.  By contrast, every single Home Depot and Ikea take unbroken CFL's for recycling.

Next, let's put the amount of mercury in perspective:

  • 3000mg - Common thermostats (max. amount)
  • 500mg - Old mercury-filled thermometer
  • 500mg - Dental filling
  • 25mg - Watch batteries from circa 1958-2008 (now going mercury-free)
  • 13.6mg - Mercury emitted at power plant to power an old NON-CFL bulb
  • <1 to 5mg - Compact fluorescent light bulb
  • <1 to 3 mg - Low-mercury CFL's (e.g., Phillips and Turolight)
  • 0.000007 mg - Median exposure from a broken CFL
    Figures from Energy Star Canada and GE, exposure figure from Illuminating Engineering Society.
See also the EPA's info about household items that contain mercury, here and here.

Let's also remember that tubular fluorescents have been used in commercial and office buildings for decades. This is not a new technology at all.

So now let's look at the politics behind all this:  I'd really like everyone to understand that the scare warnings about mercury in CFL's have been coming from Republicans who want to fight conservation.  This isn't partisan bickering, it's a matter of public record, as we'll see presently. What's especially ridiculous about this is that the GOP has fought tooth and nail against pollution controls for decades, and now they have the gall to claim to be concerned about toxic mercury.  Please.  Their real goal is to keep us from saving energy.

Think I'm exaggerating?  Here's the proof.  Rep. Ted Poe (R-TX) took the floor of the House to blast CFL lightbulbs and opened up with this flabbergasting statement:

"Congress passed an energy bill which should have been called the 'Anti-America NON-Energy Bill' because it punishes Americans for using energy, rather than finding new sources of affordable energy."

There you have it.  Any attempt to reduce our energy use isn't just unnecessary, it's supposedly anti-American!  And reducing energy use (and therefore pollution) is tantamount to punishment.  Punishment!  Since Poe is an unabashed enemy of conservation, is it any freaking wonder that he opposes energy-saving light bulbs?!  Is it any surprise that he will bring up any possible defect he can find in CFL's in order to further his anti-conservation agenda?

It gets richer. In Poe's mind, all we need to do is magically find some new sources of affordable energy.  And what do you think he has in mind?  Why, drilling the Artic National Wildlife Refuge and America's beaches for oil, for starters, something the GOP has been eager to do for years.

Anyway, when Poe has made his anti-environmental agenda so clear and plain, are we really supposed to take him seriously when he starts frothing about the environmental calamity posed by mercury in CFL bulbs?  Not.  Republicans vote consistently against any measure to reduce pollution in general, and mercury specifically.  If they're so concerned about mercury exposure with CFL's, why are they voting against measures to reduce mercury pollution? As soon as Rep. Poe and his cohorts vote for any other measure to reduce Americans' exposure to toxins, that's when I'll start taking them seriously.

On the 2007 House energy bill, which CFL's were a part of, 221 Democrats and only 14 Republicans voted for it. Of the "No" votes, over 96% were cast by Republicans. (USA Today)  And congresspersons who voted against clean energy took four times as much money from oil companies than those who voted in the public interest. (Oil Change InternationalIf you're a Republican and you're offended by my pointing out that Republicans having been fighting conservation on spurious grounds -- then please get your fellow Republicans to stop fighting conservation on spurious grounds.  Don't get mad at me for simply pointing out what's actually happening.  Because if the GOP wasn't being completely ridiculous about this issue, then I wouldn't be pointing out that they're being completely ridiculous about this issue.  It's not my fault they're being unreasonable, I'm just the one pointing it out.

And for all those who are trying to pin CFL's on Obama, the bill was passed in 2007, and signed into law by that notorious socialist, George W. Bush.

More on mercury in CFL's:


CFL's and electromagnetic fields (EMF)

See my separate page about CFL's and EMF.

Does bad power factor negate the environmental savings?

No, it doesn't. CFL's do have a bad power factor (50-60%, compared to 100% for regular bulbs), and so some have suggested that the utility company has to generate more electric to power the CFL's, even if the home user isn't charged for it, and so we don't really succeed in burning less fuel at the power plant. The truth is that while low power factor does require the utility to compensate a little bit, it's at a far, far lower level than would be the case if they had to make up the total difference between the actual power factor and a power factor of 1.  For example, here in Austin, Texas our utility is publicly-owned, and they've been aggressively pushing conservation for years to try to prevent having to build an expensive new power plant.  They hand out cold, hard cash for things like recycling your old refrigerator, installing extra attic insulation, putting in solar water heaters, and -- you guessed it -- switching to CFL's.  If CFL's didn't really save electricity even at the power plant then there's no way they'd be doing this.

Dennis Towne, an electrical engineer, agrees that low CFL power factor doesn't negate the energy savings :

"[Bad power factor] causes higher current flow than would be expected for a given power output, but it does NOT increase the power consumed.... [We can now] peacefully ignore the power factor issues of CFL's."

Josey Paul, in a letter to Home Power magazine, also agrees:

"[I]t is not true that utilities must therefore burn twice as much coal or cook twice as many atoms in order to supply twice as much energy to run Carol's CFLs. Power factor does not affect the energy consumption of homes either on or off the grid.... To prove this point, I set up an experiment with CFLs vs. incandescent lights (resistive loads with a power factor of 1.0), and measured watts and volt-amperes delivered by my inverter. Then I measured the amps from my power source, a bank of L-16 batteries, which are DC sources wise to the tricks of reactive power....The low power factor did not require the batteries (or the utility) to produce any extra energy."

Related pages

Last Update: July 2013

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