When I extolled the virtues of LED lights for the holidays despite their additional cost, most of the sets I found online were $15 for 100 lights. But sustainability engineer Pablo Paster is a better shopper. In his Ask Pablo blog, he says he found them at Costco for as little as $7.39.
Also, the Electric Power Research Institute, the utility industry's research arm, did testing at their Living Laboratory for Energy Efficiency in Knoxville, Tenn., and documented energy savings much higher than the 80 to 90 percent figure most people use. EPRI says Chevy Chase's Clark Griswold character in the 1989 movie Christmas Vacation, who lit his house with 25,000 bulbs, could have cut his electricity bill from $2,400 to $50 had he used energy-efficient C9 LED bulbs. By the way, his upfront cost, if he could have gotten them at Costco at the same price Paster found, would have been $1,847.50. So Chevy/Clark would have had his payback ($502.50 in savings, actually) in one joyful season.