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Fluorescent Lighting

Fluorescent lamps use 25%–35% of the energy used by incandescent lamps to provide the same amount of illumination (efficacy of 30–110 lumens per watt). They also last about 10 times longer (7,000–24,000 hours).

The light produced by a fluorescent tube is caused by an electric current conducted through mercury and inert gases. Fluorescent lamps require a ballast to regulate operating current and provide a high start-up voltage. Electronic ballasts outperform standard and improved electromagnetic ballasts by operating at a very high frequency that eliminates flicker and noise. Electronic ballasts also are more energy-efficient. Special ballasts are needed to allow dimming of fluorescent lamps.

Improvements in technology have resulted in fluorescent lamps with color temperature and color rendition that are comparable to incandescent lamps.

Types of Fluorescent Lamps

Two general types of fluorescent lamps include these:

You can use the chart below to compare these types of lamps. If you don't already, it helps to understand basic lighting principles and terms before making comparisons.

Fluorescent Lighting Type Efficacy
Color Rendition Index
Color Temperature
Straight tube 30–110 7000–24,000 50–90 (fair to good) 2700–6500 (warm to cold) Indoors/outdoors
Compact fluorescent lamp (CFL) 50–70 10,000 65–88 (good) 2700–6500 (warm to cold) Indoors/outdoors
Circline 40–50 12,000     Indoors

U.S. Department of Energy
1000 Independence Avenue, SW
Washington, DC 20585
www.eere.energy.gov www.energy.gov