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Matching replacement lightbulbs to existing fixtures and ballasts can be tricky, especially with older fixtures. Using new fixtures made for new lightbulbs gives you the greatest energy savings, reliability, and longevity compared with simply replacing bulbs.

Before replacing a lightbulb and/or ballast in a light fixture, it's a good idea to first understand basic lighting principles and terms. This understanding will help you make the most economical purchase.

Replacing Incandescent Lightbulbs and Ballasts

Many older indoor lighting fixtures trap a significant portion of light inside the fixture. Newer incandescent fixtures are designed to push all their light out into the room. Others use smaller halogen lights. Advances in indoor fixture design include brighter reflectors and better reflecting geometry.

Many incandescent bulbs also are mismatched to their tasks or application. For example, some outdoor fixtures tend to disperse much of their light beyond the intended area, which causes light pollution. This can be corrected by using bulbs with smaller wattage.

You can replace standard A-type lightbulbs with more energy-efficient options such as CFLs, LEDs, and energy-saving (halogen) incandescents.

Use CFLs packaged as ellipsoidal reflectors (type-ER) in recessed fixtures. Use reflector (R)or parabolic reflector (PAR) CFLs for flood and spotlighting. Some CFL fixtures have built-in electronic ballasts and polished metal reflectors.

When used in recessed fixtures, A-type and reflector lightbulbs waste energy because their light gets trapped in the fixture. To save energy, you could replace a 150 watt (W) standard reflector with a 75W type-ER. Remember, though, that ER lamps are less efficient at delivering light from shallow fixtures, so use reflectors or parabolic reflectors for these purposes.

Replacing Fluorescent Lightbulbs and Ballasts

Although fluorescent lightbulbs are generally energy efficient, there are new, even more efficient bulbs that use better electrodes and coatings than older ones. These bulbs produce about the same lumen output with substantially lower wattage.

You can replace common 40 watt (W) and 75W incandescent lightbulbs with energy-saving lamps of 34W and 60W, respectively. Energy-saving lamps for less-common fluorescent fixtures are also available.

If you need to replace the ballasts in your fluorescent fixtures, consider using one of the improved varieties. These fluorescent ballasts, called improved electromagnetic ballasts and electronic ballasts, raise the efficiency of the fixture 12%–30%.

Newer electromagnetic ballasts reduce ballast losses, fixture temperature, and system wattage. Because they operate at cooler temperatures, they last longer than standard electromagnetic ballasts.

Electronic ballasts operate at a very high frequency that eliminates flickering and noise. They are even more efficient than improved electromagnetic ballasts. Some electronic ballasts even allow you to operate the fluorescent lamp on a dimmer switch, which usually is not recommended with most fluorescents.

Fluorescent Lightbulb Disposal

All fluorescent lights contain small amounts of mercury. Some compact fluorescent lamps (CFLs) with magnetic ballasts contain small amounts of short-lived radioactive material. Because of these hazardous materials, you should not toss burned-out lamps into the trash.

Find out if there is a recycling program for them in your community--they are becoming more common, and many retailers will recycle CFLs for free. You can also dispose of the bulbs with other household hazardous wastes such as batteries, solvents, and paints at your community's designated drop-off point or during a designated day when you can put such materials with your curb-side trash pickup. See the EPA recommendations for cleanup and disposal steps.