Energy Star is an Environmental Protection Agency and U.S. Department of Energy program that rates appliances for energy use. The standards for Energy Star ratings vary by product, but in general an appliance needs to be more efficient than its conventional counterparts to receive the Energy Star rating. For example, an Energy Star refrigerator has to use at least 20 percent less energy than other refrigerators on the market [source: Energy Star].
When you do need to replace older appliances in your home, an Energy Star model can help reduce your power bill, but there is some debate about whether it's better to replace old appliances or wait for them to break before replacing. If your goal is to reduce your overall footprint, you can actually reduce your impact by running those old appliances into the ground before replacing, because the materials and shipping costs for a new appliance outweigh the potential energy savings [source: Reichman].