While using a clothesline to dry your clothes is the most energy-efficient way of drying laundry, using a gas or electric dryer is the best way of doing it.

Dryers don't vary much in energy consumption from model to model, but there are other factors to consider before you buy one.

• Need to know: A dryer's efficiency is measured by the "energy factor." The energy factor is similar to the miles-per-gallon rating of a car. Energy factor is measured in pounds of clothing per kilowatt-hour of electricity. This means the more clothes you can dry per kilowatt-hour, the less your dryer will cost you to run. The minimum energy factor for a standard-capacity electric dryer is 3.01, according to several major manufacturers.

For gas dryers, the minimum is 2.67, based on a natural-gas equivalent of the same kilowatt-hour measurement used for an electric dryer.

• Be sure to ask: What is the dryer's drum capacity? Drum capacity for a full-size dryer is 5 to 7 cubic feet, and you'll want to coordinate it with the capacity of your washing machine. A washer with a 3.5-cubic-foot capacity requires 7 cubic feet of dryer capacity.

• Operating manual: All dryers use heat to extract moisture from clothes as they tumble — and the amount of work the dryer has to do depends, of course, on the amount of water remaining in the clothes. Newer dryer models aim to minimize running time. The best models have moisture sensors in the drum that can save you up to 15 percent of drying time, but most models estimate dryness by sensing the temperature of the exhaust air.

Look for a dryer with a cycle that includes a cool-down period, sometimes known as a permanent-press cycle. In the last few minutes of this cycle, cool air rather than heated air is blown through the tumbling clothes to complete the drying process.

• Gas versus electric: Every dryer uses a small electric motor to turn the drum so the clothes can tumble. All have electric fans to spread the heated air evenly. That's where the similarities between gas and electric dryers end.

Electric dryers supply heat through coils that require a 240-volt current to work. The typical outlet is 120 volts, so you will likely be calling your favorite electrician to make the necessary change. Gas dryers use a burner to create heat; for one of these, you'll need a gas hookup, a safe way to vent the gas, and a 120-volt electric outlet for that blower and the fan.

If your laundry room is set up for both gas and electric, consider price. Gas dryers cost $50 more than similar electric models, but in many areas, natural gas is less expensive than electricity, so you could recoup the extra costs over the life of the dryer. (The typical dryer lasts about 18 years.)

• The combo washer and dryer: A few manufacturers have produced all-in-one washer/dryers that are designed to get Johnny's dirty soccer uniform in and out in record time. They are kind of pricey.

• What will it cost: Standard-capacity electric dryers cost $200 to $1,000; gas models range from $250 to $1,100. Compact dryers range from $200 to $700. These space-saving units can be stacked on top of companion washers that often work like regular-capacity models, so they need a 240-volt line. There also are combination washers and dryers on the market that do both jobs in a single machine.