Maybe this scene sounds familiar: It’s Thanksgiving, you’re sitting and watching the football game, and you want a beer. So what do you do? If you’re like many Americans, you won’t go over to the kitchen fridge, which is now crammed with leftovers. Rather, you’ll trek down to the basement or out to the garage to the second refrigerator (aka, the “beer fridge”).

Sure, it’s convenient. But the growing trend of having second refrigerators is a major national energy blight — not only wasting a lot of energy, but also potentially costing you hundreds of dollars.

From an energy standpoint, second refrigerators are bad news. The simple reason? They tend to be ancient. In fact, nearly 15 percent of U.S. homes have a second refrigerator that is at least 20 years old, which means it is virtually certain to be an energy hog when compared with today’s models.

Refrigerators are an appliance category that has seen very dramatic strides in energy efficiency in recent years, thanks to an ever tougher set of state and national energy standards, most recently tightened by the Department of Energy in September. “A fridge that just meets the new standards will use $215 to $270 less per year in electricity than a comparable unit that met the first state standards set in 1978,” writes Marianne DiMascio of the Appliance Standards Awareness Project (ASAP).

Here’s a chart, from the ASAP, showing just how dramatic progress has been. As you see in the blue line, our fridges are bigger today. Yet as you seen in the red and green lines, both the cost and the amount of energy they consume have declined dramatically.