When you replace incandescents with CFLs, you use less electricity for lighting, but you use more energy for heating your home in the winter, since hot burning incandescents–which produce a lot more heat than light–decrease the heating load. This is called the take-back effect. Anil Parekh, who does research for Natural Resources Canada, and his colleagues, studied the take-back effect. They wanted to know if CFLs really saved energy in a home over the course of a year.

The Canada study, which took place at the Canadian Center for Housing Technology (CCHT)–two identical homes that allow researchers to compare different technologies–showed that even in heating dominated climates, such as in Fairbanks, Alaska, you save energy overall by swapping out incandescents with CFLs. And in cooling climates, such as in Los Angeles, you save on lighting electricity and there is an added bonus (as if Southern Californians deserved it) you use less to cool your home in the summer, since cool CFLs, which put out 90% less heat than incandescents, are not adding to your cooling load.

Some readers may have noted that I declared my allegiance to light-emitting diodes (LEDs), in a recent blog, since they are potentially much more energy efficient than CFLs. But we'll have to live with CFLs until LEDs become more cost effective… kind of like driving my pretty-fuel-efficient 1997 Geo Prizm into the ground before investing in a newer, hybrid car, or until I quit driving. It takes a lot of energy to make a hybrid car.

Sometimes the most efficient car, or appliance, or light bulb, is the one that's already been made.

Philips Lighting was the first manufacturer to commercialize CFL bulbs in the 1970s, and has long been an innovator, as well as being the largest manufacturer of lighting products in the world. "We aren't even near the limits to this technology," said Dowling. Technically, solid-state lighting, or LED lighting, is ready to be the next big thing after CFLs. The challenge that remains is making LED lighting affordable and ubiquitous. That is a challenge when you consider that today's incandescents work in 1880s-style fixtures. Dowling proved it in a backroom of the Smithsonian in Washington D.C. And in the progressive Pacific Northwest, after 15 years on the market, CFLs have achieved only 8% market penetration.

But LEDs are an easy sell. Compared to incandescent lights, which produce 10–12 lumens per watt (lpw), and fluorescents, which produce 90-100 lpw, the best LEDs produce approximately 100 lpw, have the potential to reach the 150–200 lpw level, can last 35 years and don't release any mercury into the environment. History has shown that the cost of LED technology has decreased, while performance has increased– both exponentially. Dowling expects LED lighting performance to continue increasing 35% per year while the price decreases about 20% per year, and that in 24-36 months LED lighting will reach the level of linear fluorescent lights in light output per watt of energy use.

LEDs have evolved from mostly lighting that attracts attention to lighting that illuminates. LEDs can produce a range of color temperatures, from cool to warm. It has been installed in the Old North Church in Boston to rave reviews from the curators of the historic church. Legislation is supporting the evolution of the lighting technology. Legislation and guidelines will raise lighting efficacy to at least 45 lpw by 2020, according to Dowling, making LEDs an easy choice.

Goodbye CFLs, it was good while it lasted.