Compact Fluorescent Lamps

Replacing incandescent lamps with high-efficiency fluorescents can reduce lighting energy costs by up to 75%. In addition, fluorescents last almost 10 times as long as incandescents for an added benefit.

Screw-in Replacements

Fluorescent lamps with incandescent-type screw-in bases or adapters fit into many incandescent fixtures. The fluorescent lamp may disconnect from the ballast for lamp replacement, or the lamp may be permanently affixed to the ballast. Several types are available.

Compact fluorescent lamps that can detach from the ballast come in 5, 7, 9, 13, 18, 22, 26 and 28 Watt sizes and plug into reusable screw-in ballast/adapters. These ballasts have a rated life of 45,000 - 50,000 hours (about 15 years based on a 5-day, 60-hour work week). Compact fluorescent lamps that detach from the ballast reduce labor costs since the ballast does not need to be discarded when the lamp burns out. Direct-wire ballast adapters are also available.

Compact fluorescent lamps may come as a complete lamp/ballast unit. When the lamps burn out, the ballast must also be replaced. However, these lamps will last about 7 to 10 times as long as standard incandescent lamps and are available in 15- to 22-Watt sizes.

A 28-Watt compact lamp provides the same amount of light as a 100-Watt incandescent, for one-third the energy cost.

The following table shows a few incandescent lamps and the suggested fluorescent replacements.

Fluorescent Replacement
40-Watt A-19* 9-Watt compact
60-Watt A-19 13 or 15-Watt compact
75-Watt A-19 18 or 20-Watt compact
75-Watt reflector 13 or 18-Watt compact, w/reflector
100-Watt A-19 28-Watt compact

*A-19 is a designation for the standard incandescent lamp shape.

Fluorescent wattage includes both lamp and ballast wattage.

In extremely shallow downlights, the fluorescent lamps may project beyond the fixture cone, creating an objectionable appearance. Try "Quads" or double twin-tubes, which produce the same light as a twin-tube at half the tube length.

Although fluorescent lamps initially cost more, they use less energy and last longer. Therefore, energy costs and labor costs for lamp replacement are reduced.

The following chart illustrates the potential savings typically expected when replacing a 60-Watt incandescent with a 15-Watt fluorescent lamp. (Note that one fluorescent lasts as long as ten incandescents). As shown, the energy costs of fluorescents is one-fourth those of incandescents and the total cost is one-half of incandescents.

Incandescent versus Compact (Screw-in ) Fluorescent
Lamp Type
Bulb Retail**
Energy Cost*
Life Cycle
60-Watt Incandescent
.06 kW x 4,000 HR x $0.06/kWh - $14
15-Watt Compact Fluorescent
.015 kW x 4,000 HR x $0.06/kWh - $4

  * 4,000 hours of operation per year; $0.06 per kWh
** Cost of incandescent bulb assumes $1.00 per bulb with a 1,000 hour life. Cost of fluorescent assumes $15 per unit with a 10,000 hour life.

Fluorescent Facts

  • Buying fluorescents in volume offers even greater savings
  • Fluorescents can reduce your cooling costs since they emit less heat
  • Screw-in fluorescents, which are somewhat larger than incandescents, come in a variety of sizes and shapes including globe, tube, and circle styles
  • Some fluorescents are heavier than traditional bulbs because they require a ballast
  • Measure a fixture before buying compact fluorescent bulbs. Fluorescents are larger and don't always fit traditional fixtures. Harp adapters can often remedy this problem.