If you’re in the market for a new home appliance and you want that purchase to be as environmentally friendly as possible, you might look for options that feature a label from Energy Star, a symbol backed by the Environmental Protection Agency and Department of Energy specifically to promote energy-efficient products. Each year, Energy Star puts out a list of the Most Efficient appliances, those that the program says “save you money and protect the environment.” The list also features the “most efficient, pollution-reducing products.” Until now, that list might have included gas-powered appliances such as gas dryers, furnaces, and...