If you know the difference between the Energy Guide label and the Energy Star label, you are in better shape than many consumers, even many energy-conscious ones. (If you can explain why it makes sense to have three different federal agencies administer two separate labeling programs with names and purposes so similar that even retailers get them confused, you’re a genius.)

The Energy Guide label is a yellow-and-black sticker or hang tag that tells consumers the estimated annual energy use and operating costs of new household appliances.

The label is legally required to be on refrigerators, freezers, dishwashers, washing machines, room air conditioners, water heaters and other products. Among other things, it includes a comparison scale that consumers can use to judge a product against similar models.

The blue-and-white Energy Star label, on the other hand, is a voluntary program available to a much broader range of products than just appliances. (It even includes buildings.) An Energy Star label identifies the product carrying it as more efficient than most of its peers. For appliances, the cut-off a product must reach varies. An Energy Star dishwasher, for example, must be 10 percent more efficient than the least efficient unit, while washing machines must be 37 percent more efficient.

Both labels have their problems. Energy Guide labels often convey outdated information that makes products appear misleadingly efficient relative to others. And they are frequently missing from products in stores and online. Energy Star labels can remain on products that no longer qualify for updated standards. And pilot testing has shown that significant numbers of products that carry the label don’t actually meet the Energy Star requirements.

Earthjustice is working to remedy these problems so that consumers can rely on these labels and receive the energy savings they expect. But knowing the difference between the two labels is half the battle.