For most homeowners, lighting is an afterthought. The pear-shaped incandescent bulb—in use since the days of Edison—remains the standard in most homes. According to the United States Department of Energy it accounts for about 85 percent of household illumination in the country.

Though incandescent is still the cheapest option per bulb, in the long run, experts agree, more efficient lighting choices can lead to significant savings and draw less on the planet’s dwindling energy resources.
The simplest way to conserve energy, said Patricia Rizzo, of the Lighting Research Center at Rensselaer Polytechnic Institute, "is not to turn the lights on at all."

Only about 10 to 15 percent of the electricity incandescent bulbs use result in light, says the Department of Energy; the rest is heat.

Since it’s not possible to have lights always off—they’re there for a reason—homeowners can save energy by turning out the lights when they leave the room. A variety of timers and automatic sensors are available to make the task of remembering easier.

In California, Rizzo said, a new law requires 50 percent of the lights in the home to be energy-efficient. The rest, she said, need to be on dimmers. By setting the light level to match the needs of the users, dimmers save energy. Rizzo expects similar requirements to come soon to other states.
"Where California goes, the country usually follows," she said.

Homeowners who are willing to make an initial investment on more efficient light bulbs could realize a healthy return.

According the the Department of Energy, fluorescent bulbs, the most popular replacement for incandescent, cost 10 to 12 times more than their counterparts, but they use 25 to 35 percent the amount of energy. One compact fluorescent lamp can replace an incandescent light of three to four times its wattage, and it will last up to 15 times longer.

While incandescent bulbs light by heating a thin filament inside a vacuum, fluorescent lights use electricity to excite a gas inside the bulb. The compact variety, with their bent tubing, are about the same size, can be screwed into the same sockets, and are usually available in the same stores as traditional light bulbs.

For many people, fluorescent lighting means flickering bulbs, an annoying whine, and harsh yellow light. These are becoming things of the past, Rizzo said.
"Fluorescents have had a bad rap all these years," she said. "Well, things have improved so much in the technology."

The replacement of magnetic ballasts, devices that control the current, with electronic ones has eliminated flicker and decreased the amount of time it takes for a fluorescent light to reach full illumiation.
The color-rendering now possible with fluorescent lighting, Rizzo said, "is beautiful."

Fluorescents are not always the answer, Rizzo said. They produce a more diffused light and can’t be easily coupled with reflectors, so they’re not appropriate for applications like recessed lighting. They also won’t work on a traditional dimmer switch.

Homeowners looking for a focused lighting choice other than incandescent, Rizzo said, might consider low-voltage halogen lights.

Light-emitting diodes (LED), long in use in signs, signals, and indicator lights, are becoming a more common source of illumination. LED have color-rendering capabilities comparable to fluorescent lights, can be dimmed, and have a high level of efficiency. Rizzo said LED will start flooding the market within the next year.

However, she said, it’s hard to compare them to other light sources, because industry standard measurements for them haven’t been set yet. It’s one of the things the Lighting Research Center is working on, she said.
"The products may not perform the way you expect them to," Rizzo said.

Finally, the most basic form of light is sometimes the best, or at least the cheapest.

Those building a new house can incorporate daylighting, the use of natural light, into their designs. For example, builders can strategically place skylights to bring sunlight into a room. Hybrid skylights combine the sun with fluorescent lights.
"Daylighting is a great way to get light in big doses," Rizzo said.