Compact fluorescents present several practical and design challenges: Some manufacturers still offer fewer fixture options for CFLs than for incandescents, the bulbs must warm up to achieve full brightness, color quality is variable, and it can be confusing for homeowners to choose the ideal color temperature. Also, quality dimmable CFLs are not only expensive, they do not dim to a warm glow like incandescents.

The environmental (and most publicized) downside of compact fluorescent lamps is their mercury content. According to the EPA, CFLs contain an average of 4 milligrams of mercury, some of which can be released into the air or water if the bulb is disposed of in a landfill and can create a health hazard if the bulb is broken inside the home. However, some manufacturers are now offering lamps with low mercury content of 1.4 milligrams to 2.5 milligrams, and a variety of retailers, including The Home Depot, offer reclamation bags in which consumers can recycle their CFLs.

Even if CFLs are sent to a landfill, they result in less mercury in the environment over the life of the bulb, the EPA states. Emissions from coal-fired electrical power are the main source of mercury emissions in the U.S., the agency explains, and CFLs save so much electricity that their mercury content is lower than that of the emissions used to power equivalent incandescent bulbs.

LEDs

A much different source of light than incandescents or CFLs, LEDs (light emitting diodes) are actually tiny, encapsulated semi-conductors that can last for 30,000 hours to 50,000 hours or more.

While LEDs are widely known as colored indicator lights in items such as computer monitors or car dashboards, in recent years manufacturers have begun to offer them in shades of white and grouped in the shape of a light bulb so they can be screwed into traditional fixtures or replace incandescent downlights. But they’ve been most successful so far as accent lights built into a fixture or surface.

While LEDs are not yet as efficient as compact fluorescents—their efficacy is between 30 lumens per watt and 60 lumens per watt—manufacturers and government researchers are investing millions of dollars in advancing them. LED efficiency is improving by about 100% every 24 months, estimates Joseph A. Rey-Barreau, a lighting designer and associate professor at the College of Design at the University of Kentucky. “In five to 10 years, it may be the most predominant light source everywhere,” he says.

At five to 10 times the cost of compact fluorescent fixtures, large LED fixtures are still out of the price range of most residential applications. But designers say they are using small LEDs in cove, undercabinet, and step lighting applications. In years to come, organic LEDs (LEDs stretched into thin films) could change the way we see lighting entirely, allowing designers to stretch a light source across a wall or ceiling and turning fixtures and sockets into a remnant of the past.

Halogen

While CFLs are generally the most energy- and cost-efficient option, they’re still not the best choice where color quality or dimmability is most important. Halogen lights, a more efficient form of incandescent, provide warm, bright light and are fully dimmable, meaning they may be best for applications such as dining rooms or reading lights where color quality is the biggest concern. Philips Lighting’s Halogena, for example, offers energy savings of about 30% over standard incandescents, and are rated to last about 3,000 hours.