“Is your refrigerator running?” is no longer the question. Instead, it’s “How much energy is it using?”

Old appliances, particularly refrigerators and freezers, suck so much power off the grid that states and utility companies often offer consumers incentives to replace them. For example, at the time of this writing Pepco was offering customers $50 for each old refrigerator and freezer they recycle, and Dominion was offering a $100 to $150 rebate to customers for purchases of eligible Energy Star-certified refrigerators.

But even after adding up any rebates you can get, from a pragmatic money-saving perspective the expense of exchanging old appliances for new ones is seldom covered by the energy savings you get. If you replace an old, inefficient clothes washer with an Energy Star-certified model, you could save $40 to $50 per year in energy and water savings—which means a new model that cost $750 would have to be used a long time for utility-bill savings to cover its cost. And Energy Star-certified dishwashers tend to save only about $10 to $20 a year more on electricity and water than non-certified models. But if your current refrigerator was manufactured more than 15 years ago, investing in a new model makes sense. According to Energy Star estimates, here are the annual energy savings from upgrading a top-freezer-model refrigerator to a new certified unit:

Made before 1980: $235
Made 1980—1989: $169
Made 1990—1992: $114
Made 1993—2000: $58
Made 2001—2008: $17

On the other hand, if your existing appliance needs repair, determine the cost of replacement minus expected energy savings versus the cost of the repair. Calculations on the Energy Star website let you compare annual operating costs of efficient and inefficient appliances according to how much you use them and how long you expect the new unit to last, among other variables.

Of course, many consumers might want to switch to energy-efficient appliances to minimize the amount of energy their homes use and reduce their contribution to pollution.

The following tips from Energy Star will minimize electricity usage, regardless of your refrigerator’s age:

  • Set the temperature of your refrigerator at 35° F and freezer at 0° F.
  • If possible, position your refrigerator in a cool place, away from your oven and dishwasher, and out of the sunlight.
  • To allow air circulation, leave a two- or three-inch space between the back of your refrigerator and the wall.
  • Make sure to maintain an airtight seal when you close refrigerator and freezer doors. When seals wear out, replace them.