Last week I admitted to finally updating my house with CFLs. This week, my partner in Weekend Winterizing challenges, Susanna Donato, talks about a different type of energy-efficient light bulb: the tiny, colorful ones we like to hang for the holidays. While my boyfriend and I share a rental and don't have the freedom to decorate the outside of our house with lights, we do have an annual holiday tradition of picking out a plucky Charlie Brown tree and rigging it with lights. (We also make our ornaments out of old beer caps.) Two years ago, Donato's family bought LED lights for their Christmas tree. Although they weren't the cheapest purchase, the Sierra Club estimates LED lights use just 10 percent of the energy of regular lights, an approximate $50 savings on electricity bills over the holiday season. Donato notes that Consumer Reports has also done a comparison of LEDs versus traditional holiday lights, finding the electricity costs to be similar, though LEDs use less energy. She also points out that this week Costco has strings of 100 white LED holiday lights for close to $15---meaning more people should be able to afford making their trees both sparkly and energy efficient this year.