Energy efficiency ratings are measurements that indicate how effectively a device or building uses energy. These ratings help consumers understand how much energy a product consumes compared to its output. Common examples include appliances like refrigerators and air conditioners, which often display their efficiency on labels such as the Energy Star certification. Higher energy efficiency ratings typically mean lower energy costs and reduced environmental impact. For instance, a home with a good energy efficiency rating may require less heating and cooling, leading to lower utility bills. Understanding these ratings can help consumers make informed choices when purchasing energy-related products.