Lighting - Light Bulbs

There are three primary types of light bulbs: incandescent, halogen, and compact fluorescent.

Incandescent Bulbs

Inside an incandescent bulb is a filament that is heated, giving off light in the process. The filament is delicate and eventually burns out. Some incandescents incorporate heavy-duty filaments or introduce special gases into the bulb to increase life. While this does not increase efficiency, it increases longevity by up to four times. Most manufacturers are not offering “energy-saving” incandescent bulbs. These are nothing more than lower-wattage bulbs marketed as having “essentially the same light output,” when in fact a lower-wattage bulb will simply result in less light. Incandescent bulbs are the least efficient type of bulb.

Quartz-Halogen Bulbs

Tungsten-halogen (or quartz) bulbs are really just turbocharged incandescents. They are typically only 10% to 15% more efficient than standard incandescents. Compared to standard incandescents, halogen fixtures produce a brighter, whiter light and are more energy efficient because they operate their tungsten filaments at higher temperatures than standard incandescents. These higher temperatures result in a greater potential for fire than with other types of bulbs. While they are slightly more energy efficient than standard incandescent lamps, they are not as energy efficient as fluorescent lamps.

Compact Fluorescent Bulbs

Fluorescent lamps are much more efficient than incandescent bulbs and last 6 to 10 times longer. Although fluorescent and compact fluorescent (CFL) bulbs are more expensive than incandescent bulbs, they pay for themselves by saving energy over their lifetime.

This table assumes the light is on for 6 hours per day and that the electric rate is 10 cents per kilowatt-hour.

  27 Watt Compact Fluorescent 100 Watt Incandescent
Cost of Lamps $14.00 $0.50
Lamp Life 1642.5 days (4.5 years) 167 days
Annual Energy Cost $5.91 $21.90
Lamps Replaced in 4.5 Years 0 10
Total Cost $40.60 $103.55
Savings Over Lamp Life $62.95 $0

Comparison of incandescent versus CFL bulbs.

A-shaped Incandescent Bulb (Watts) Equivalent CFL Bulbs (Watts) Typical Lumens (Measure of Light Output)
40 15 > 450
60 20 > 800
75 25 > 1,100
100 30 > 1,600
150 50 > 2,600

What to look for in a CFL: a CFL lamp that uses 1/3 the wattage of your current incandescent bulb, a lamp that fits your shape, size, and configuration requirements, a color temperature which replicates your current lighting, a system with a power factor equal to or greater than 90%, a system with a total harmonic distortion rating of 33% or less, a lamp with 10 mg or less of mercury, and a lamp without any radioisotopes.

Bulb Purchasing Considerations

If every household in the U.S. replaced one light bulb with an ENERGY STAR labeled compact fluorescent light bulb (CFL), it would prevent enough pollution to equal removing one million cars from the road. CFLs provide high-quality light, smart technology, and design, requiring less while lasting longer than typical incandescent bulbs.

ENERGY STAR qualified CFLs use 66% less energy than a standard incandescent bulb and last up to 10 times longer. Replacing a 100-watt incandescent with a 32-watt CFL can save you at least $30 in energy costs over the life of the bulb.

ENERGY STAR qualified CFLs operate at less than 100F, they are also safer than typical halogen bulbs, which are frequently used in floor lamps or torchieres and burn at 1,000F. Due to their high heat output, halogens can cause burns and fires. CFLs are cool to the touch.

ENERGY STAR labeled CFLs provide the same amount of light (lumens) as standard incandescent bulbs, but have lower wattage ratings. This means they use less energy and cause less pollution. If you are unfamiliar with the best wattage to use, use the table below to help you determine the correct CFL replacements for the incandescent bulbs.

Where electricity is produced from coal - and most is - each CFL will cut carbon dioxide emissions by about 1,300 pounds over its lifetime. Investing in a CFL provides a risk-free return of 25-40% a year. By paying $15-20 initially for an 18 watt CFL, consumers can avoid buying ten ordinary 75 watt bulbs and save about $35 in electricity costs over the life of the CFL. Similarly, by switching from incandescent lighting to compact fluorescent lighting the average consumer can save 50-80% in energy costs without any loss in lighting quality. Also, the average CFL bulb lasts 8 to 10 times longer than any incandescent bulb.

Depending on the initial cost of the bulb, the Federal Trade Commission estimates that it costs $2.60 less per year to power a compact fluorescent bulb than an incandescent bulb and are about 3 to 4 times more efficient than incandescent bulbs. The full purchase price will be paid back well within the 10 year life expectancy.

A CFL can be found for just about every lighting need. They range in size from 4.5 to 22.5 inches, in power from 5 to 55 watts and in light output from 250 to 4,800 lumens. The average lifetime ranges from 8,000 to 20,000 hours based on three hour uses in each cycle.

Electronic ballast systems lose 20% less energy than those that are magnetically ballasted.

A CFL rated at 20 watts can easily replace an incandescent of 60 watts - a 3:1 ratio.

Contact your local utility company to inquire about rebate options.

Mercury is used to provide fluorescence in light bulbs. Incandescent bulbs are responsible for releasing more than twice as much mercury into the environment than CFL bulbs.

Some bulbs used in magnetic ballasts contain certain radioisotopes such as Krypton-85, Promethium-147, or Tritium. There are bulbs available, however, that do not contain any presence of these.

Suggested Products

Success Story

Mount Sinai Medical Center in New York recently replaced standard fluorescent tubes and incandescent lamps in one of its facilities with high-efficiency fluorescent lamps, electronic ballasts, and new reflectors. As a result, lighting energy use in the one million square foot facility was cut almost in half, saving $485,000 per year and yielding a 45% annual return on a $1,086,000 investment.


A new type of CFL-Cold Cathode Fluorescent Light (CCFL) - has been developed. CCFL bulbs are even more efficient, produce less heat, and are smaller and more compact. They are also projected to last much longer than conventional CFL bulbs and ballasts. CCFLs may be available for sale in the near future.


Linear Fluorescent Luminaires

A large portion of the commercial and industrial lighting systems currently in use was put in place between 1960-1990. The systems that are in place often rely on the use of manually controlled incandescent and standard fluorescent lighting with magnetic ballasts, or even mercury vapor systems. These types of lighting systems and lighting controls are generally less efficient than those currently available, which include full-size and compact fluorescent systems with electronic ballasts, low-wattage high intensity discharge systems, and more advanced controls and sensors.

New lighting and control systems not only offer greater lighting comfort and productivity, but also longer lifetimes and reduced maintenance. Most importantly, these new luminaires and control systems combined are extremely efficient. Reducing the incandescent and fluorescent lighting systems of ten or fifteen years ago with these new systems can cut lighting energy use in half or more.

There is much more than could be and has been written about this subject. But given the time constraints of this project, this will have to suffice.


U.S. Department of the Interior

Greening of the Interior