The U.S. Department of Energy launched its "Change a Light, Change the World" 2007 campaign Wednesday during a Salt Lake City ceremony.

U.S. Assistant Secretary for Electricity Delivery and Energy Reliability Kevin Kolevar officiated at the event at an elementary school, encouraging citizens to change at least one incandescent light in their home to a compact fluorescent bulb.

He said CFLs use 75 percent less energy than do standard bulbs, while lasting up to 10 times longer, resulting in fewer greenhouse gas emissions and substantial energy cost savings.

The campaign includes an online pledge to use CFLs at home. The Energy Department said more than 500,000 people have taken the pledge.

Kolevar noted lighting accounts for nearly 20 percent of the average home's electric bill and each CFL can save up to $30 in energy costs during its extended lifetime by using 75 percent less energy than a traditional bulb.

Critics, however, warn such bulbs contain small amounts of mercury, a neurotoxin, and might break, possibly contaminating consumers or the soil.