Replacing incandescent lighting with energy-efficient alternatives could save the United States $9 billion a year and avoid the carbon dioxide emissions of 11 million midsize cars, says a United Nations report.

Energy-efficient lighting could save $5.5 billion a year in China, which uses 12% of its electricity for lighting, $1 billion annually in Indonesia and $900 million in Mexico, according to an analysis of 100 countries by the U.N. Environment Programme and the Global Environment Facility. These groups, working with lighting companies Osram and Philips, released the findings this week at the U.N. climate change summit in Cancun, Mexico.

Worldwide, a shift from incandescent lamps to efficient alternatives would reduce electricity demand for lighting by more than 2%, the U.N. reports.

"In reality, the actual economic benefits could be even higher," Achim Steiner, U.N. Under-Secretary General and UNEP executive director, said in a statement. "A switch to efficient lighting in Indonesia, for example, would avoid the need to build 3.5 coal-fired power stations costing U.S. $2.5 billion and similar findings come from other country assessments."

"Among the low hanging fruit in the climate change challenge," he added, "a switch to far more efficient lighting must rank as among the lowest."

Follow Green House on Twitter

Yet despite these environmental and economic savings, the study says incandescent lamps account for 50% to 70% of lighting sales worldwide. It notes, however, that about 40 countries including the United States currently have plans to phase out old bulbs.

Unlike incandescent light bulbs, which produce 95% heat and just 5% light, the study says compact fluorescent lighting produces the same amount of light using 75% less energy and lasts up to 10 times longer. It says the mercury in CFLs can be safely disposed of and poses far less of an environmental threat than that generated by coal-fired plants needed to power less efficient lighting.

It cites a recent study by Yale University showing that if the United States switched to CFLs, the energy savings at power stations would lead to cuts in mercury emissions of 25,000 tons a year.

The U.N. report cites the falling prices of CFLs, now about four times that of an incandescent bulb, and the growing availability of other alternatives, including LEDs or Light Emitting Diodes. For the second year, the National Christmas Tree -- unveiled this week by President Obama on the south lawn of the White House -- is lit by LEDs.