The newest energy-saving stars on the holiday scene are Holiday lights made with light-emitting diodes, or LEDs. First introduced in 2001, LEDs incorporate the same computer-chip technology used to light calculators and watches. The lights, which use semi conducting material rather than incandescent filaments, are 90 percent more efficient than traditional Holiday lights. According to one U.S. Department of Energy study, if everyone replaced their conventional holiday light strings with LEDs, at least two billion kilowatt-hours of electricity could be saved in a month. The savings would be enough to power 200,000 homes for a year.