If you want to lower utility bills and limit your use of polluting energy sources, replacing your home refrigerator is a wise choice. Refrigerators and freezers account for nearly 17% of a home's energy use, more than any other appliance.

You should especially think about getting a new unit if your current one is more than 20 years old. Refrigerators have become 60 percent more efficient since then.

ENERGY STAR, a program funded by the U.S. Dept. of Energy and Environmental Protection Agency, sets the benchmark for energy-saving appliances.

ENERGY STAR-approved refrigerators are at least 15 percent more efficient than the federal standards dictate. Compact refrigerators and freezers (smaller than 7.75 cubic feet) use at least 20 percent less energy than the government standards. They must have the best compressors, insulation, and temperature and defrost regulators.

When shopping for a refrigerator and freezer in a store or online, check ENERGY STAR's yellow EnergyGuide label. It estimates how much energy will be used in operating the appliance (in kilowatt hours) and how much this will cost. There's also an efficiency comparison with other models in the same class.

It doesn't pay to get the cheapest refrigerator if it doesn't work efficiently.

"Always keep in mind that appliances have two price tags," said the California Energy Commission's Consumer Energy Center. "One tag is the purchase price on the equipment when you pick it out at the store. The other price is the operating cost paid out month after month, year after year, in the form of your electricity bill."

You want to get a refrigerator and freezer that's just the right size for your family. The larger the unit, the more energy it will take to cool it. That said, if your appliance is too small, you'll likely have to drive to the food store more often (which isn't very efficient). It's also better to have one big refrigerator than two small ones in terms of energy savings.

The most efficient refrigerators, according to ENERGY STAR, are about 16-20 cubic feet in volume. Top or bottom freezers use up to 25 percent less electricity than side-to-side models. (Freezer-below-the-refrigerator units seem to be better.) But stand-alone chest freezers have the most energy savings because they're well insulated.

Automatic icemakers and in-the-door water and ice dispensers are convenient features, but they can increase the retail cost by hundreds of dollars and waste about 17 percent more energy.

A mini refrigerator door, however, helps to reduce cooling costs because it allows access to your most used food items (milk, orange juice, bread, etc.) without having to open the primary door.

Models with automatic moisture control are beneficial because they prevent condensation on the outside of the unit (without a heater). While the "anti-sweat" heater wastes up to 10 percent more electricity (though this feature can be deactivated with an "energy saver" button).

Manual defrost freezers use half as much energy as automatic defrost units. But this savings is only realized if the manual version is defrosted every so often so the motor isn't hindered by thick frost.

The most energy-saving appliances can sometimes qualify for rebates from utility companies. (Check with your local electricity provider.)

Once at home, there are many ways to make new and old refrigerators more efficient.

Your refrigerator thermostat should be set between 35 and 38 degrees Fahrenheit and your freezer between 0 and 5 degrees Fahrenheit.

Avoid putting your refrigerator and freezer in a warm location next to the stove, dishwasher or in direct sunlight for most of the day. (Leaving your refrigerator in a garage that isn't insulated can be a real energy waster, especially during the summer. The appliance uses up to 50 percent more electricity when the room temperature is 90 degrees versus 70 degrees Fahrenheit.)

It's a good idea to leave room for air to circulate between the condenser coils at the back of the refrigerator and the wall or cabinets (so heat doesn't build up). You should dust or vacuum the coils occasionally, too.

Not sure whether to get rid of the old refrigerator?

If it's more than 15 years old, you probably want to replace the unit.

Refrigerators built pre-1993 often cost $50 more to run per year, while ones that are pre-1980 cost $150 more to run per year compared with the current efficient models. ENERGY STAR actually has a calculator on its Web site that determines how much an old appliance costs to operate.

Over time, the refrigerant goes bad and the door seals leak cold air. One way to check the seals is to close a dollar bill in the door. If the bill falls down, then you're throwing away a lot of money. (An alternate method is to put a flashlight in the unit shining toward the door seal. In a darkened room, if you can see light coming from the refrigerator, you'll know there's a leak.)

[See the American Council for an Energy-Efficient Economy's guide.]

The Steel Recycling Institute maintains a list of refrigerator and freezer recyclers. Additionally, your utility company may take away an old unit for free (and even pay you for it).

Since your refrigerator and freezer need to run all the time (at least for food to stay fresh), you might as well find the most energy-efficient appliance that suits your household's needs.

For some energy-efficient refrigerator options, try these from The Home Depot.