Why do some appliances have Energy Star stickers? How do they relate to the yellow and black EnergyGuide stickers?
Energy Star is a voluntary program jointly developed by the U.S. Environmental Protection Agency and the U.S. Department of Energy. To earn an Energy Star label, appliance manufacturers must meet the minimum standards set by the program (which exceed the efficiency of standard products) and apply for the label. This means that there may be other appliances that meet or exceed the efficiency of Energy Star-labeled models, for which the paperwork is not done. On the Energy Star website, you can find What Makes a Product ENERGY STAR? and a current list of ENERGY STAR Qualified Products.
The familiar yellow-and-black EnergyGuides have more legal clout, as they are required by the Federal Trade Commission (FTC) on clothes washers, dishwashers, refrigerators, freezers, water heaters, window air conditioners, central air conditioners, furnaces, boilers, heat pumps, and pool heaters. (They are not required for other household appliances such as ranges, ovens, clothes dryers, humidifiers, and dehumidifiers.) The labels provide an estimate of the product's energy consumption or energy efficiency, the highest and lowest energy consumption or efficiency estimates of similar models, and the estimated yearly energy costs to operate. The appliances with these labels may or may not also have Energy Star labels. The FTC also requires energy disclosures for certain lighting products and water use labeling for certain plumbing products.
"How to Buy an Energy-Efficient Home Appliance" discusses the two labels (EnergyGuide and Energy Star). Federal Trade Commission in cooperation with the U.S. Department of Energy, June 2000.