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How Many Crotonites Does it Take to Change a Lightbulb?

October 24, 2007


compact flourescent light bulbs

If every American home replaced just one light bulb with an ENERGY STAR qualified bulb, we would save enough energy to light more than 3 million homes for a year, more than $600 million in annual energy costs, and prevent greenhouse gases equivalent to the emissions of more than 800,000 cars.

Turning off lights and appliances not in use is one great way to conserve. Using more energy efficient lights and appliances is another. Take the pledge and learn more today at “Change A Bulb.”


CFL bulbs use one fifth to one quarter of the electricity of an equivalent incandescent bulbs. An 11 to 14 watt CFL bulbs gives the same light output as 60 watt incandescent bulb. And CFL bulbs last 6 to 15 times longer than incandescent bulbs and have no delicate incandescent filament to burn out.


CFLs are fine in all common light fixtures that presently use incandescent bulbs. They will yield the greatest savings, and avoid problems, if they are installed in indoor sockets where (a) lights are kept on for more than just a few minutes at a time (i.e. most locations except closets) and (b) lights are not controlled by motion sensors or photocells. They will work in outdoor sockets, but may not be as bright as expected when it gets very cold. Their long life makes them especially useful for hard to reach light fixtures.

How do I read the label on CFL bulb packages?

How to read a compact fluorescent lamp label (pdf)

So experiment! CFL manufacturers are producing ever higher quality CFL bulbs with quite a wide array of colors of light, as we can see in this photo. Most of us will find 8 to 10 fixtures in our homes that are well suited for CFL bulbs.

Want more background on CFL bulbs?

An incandescent bulb creates light by heating up a thin wire until it and the air around it glows. So these bulbs give off both light and heat. In fact, most of the electricity consumed by incandescent bulb turns into heat, not light. Only a small fraction of those kilowatts become incandescent light.

CFL bulbs create light by energizing the gas inside. Most of the electricity consumed by a CFL produces light with very little heat production, mainly from the bulb’s ballast that ionizes the gas. The gas in CFL bulbs radiates at a certain wavelength which determines the color of the light we see. Good quality CFL bulbs contain 3 or 4 different phosphors, each radiating a light of a different color. So look for good quality bulbs with the Energy Star certification.

In the past few years, the major manufacturers have all put out an astounding array of CFLs to match the color of light you prefer (cooler blues to warmer yellows), the size of your existing fixture’s socket (check out the new mini-CFL bulbs) and the shape you need (from little corkscrew to outdoor spotlight).

From left to right, the bulbs in this photo are: a 13 watt GE CFL emitting 6500 K; a 60 watt Sylvania incandescent soft white emitting c. 3000 K; a 15 watt Bright Effects CFL emitting 2644 K; and a 14 watt Sylvania CFL emitting 3000 K. “K” stands for Kelvin degrees which is a way to measure color (see the spectrum image below).


Nonetheless, the color of light from most CFL bulbs does not contain the full spectrum of visible light that incandescent bulbs shed. That smaller color range might affect where you would use CFLs. You may want a warmer, yellower light in your favorite reading lamp than a CFL bulb can provide.

Some CFL manufacturers state the color emitted by the bulb in degrees Kelvin. The higher the Kelvin number, the cooler (bluer) the light will be. Incandescent bulb (tungsten) filaments emit around 2800 Kelvin. Moonlight is around 4100 Kelvin. Typical “warm” daylight is around 5000 Kelvin.

While CFLs may start at low temperatures, they take about 20 seconds to reach ~75% output. Most incandescent lamps reach full brightness almost immediately. If you need immediate full brightness, e.g., during a short visit to a closet or bathroom, an incandescent may still be more appropriate than a CFL bulb.

Likewise, CFLs used outdoors in winter may not yield equivalent or full brightness. The fluorescent process yields its peak output chiefly within a relatively narrow temperature range (between ~57°F to ~97°F). Air temperatures higher or lower than this range result in less light from the CFL bulb. So, in the Northeast, CFL bulbs burn brightest at the indoor temperatures common inside most homes.

Do not install CFLs in any light fixtures controlled by dimmers without first checking with an electrician to be sure that a dimmable CFL will work with your dimmer. Normal CFL bulbs can not be used in dimmable fixtures. If you have recessed fixtures, try special CFL reflector bulbs.

CFL bulbs do not give off nearly as much heat as incandescent bulbs. So you may want to stay with incandescent bulbs where you want heat plus the light, like for the box where your kids are raising baby chickens!

Leo Wiegman

Editor’s note: The author is a former Village of Croton-on-Hudson Trustee who served three terms from 2001 to 2007.

Image sources: The first two images are from, the PDF label guide from; The remaining images come from and related links (and are subject to license restrictions noted there).

On October 27, 2007 3:11 PM, Leo Wiegman said:

Dear Gut-C: Good question! As I mention in the PDF attached above: CFL bulbs do contain a trace amount of mercury. Disposing of these bulbs must be done properly. Keep your old CFL bulbs in a box, along with your old batteries. Then dispose of them at the County’s Household Chemical Clean-up Days. Read more details at

Find more info about recycling CFLs and other kinds of lamps at

PS. The filament in an incandescent bulb is made of tungsten, a rare and valuable metal. We toss out those bulbs without thinking about it. Today’s landfills will be rich, messy depositories we will mining for raw materials some day.

On October 25, 2007 6:59 PM, Gut-C said:

Thanks for all the info, Mr. Weigman. Can you add a new comment on how to dispose of these bulbs? I know for sure you SHOULD NOT just toss them in with your trash. CFL’S contain chemicals that should not be discarded with regular trash.


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