Heat pump clothes dryers explained

About 80% of American homes have a clothes dryer. A conventional dryer heats air, blows it through the clothes and pushes the hot, damp air outside through a vent. A heat pump dryer keeps its air instead. It works as a closed loop, heating the air, using it to pull moisture from the clothes, then passing that humid air through a condenser that removes the water without losing much of the heat. The same air goes around again.

What that changes

• Energy. Heat pump dryers use around 70% less energy than conventional dryers, and every one meets the criteria for ENERGY STAR Most Efficient.
• No vent. Because no air goes outside, a heat pump dryer doesn't need a dryer vent. In a home without one, that saves the cost of putting a vent in.
• Water to drain. The water the condenser collects has to go somewhere. It either runs to a drain or collects in a tank that has to be emptied. Some models can use the clothes washer's drain.
• Refrigerant. Like any heat pump, it uses a refrigerant. Some, such as R-290, have a much lower global warming potential than others.

Features many efficient dryers share

• Moisture sensors. They stop the dryer when the clothes are dry, which saves energy and cuts the wear that over-drying causes.
• Lower heat. Efficient dryers generally dry at lower temperatures than standard ones.
• Delayed start. It lets the dryer run later, which can lower the cost where a utility charges different rates at different times of day.

Keeping any dryer efficient

• Load size. A load too big takes longer to dry. A load too small wastes energy, since drying one towel for 30 minutes costs about as much as drying a full load for the same time.
• The lint filter. Clean it after every load. It keeps air moving, makes the dryer more efficient and is an important safety step.
• Dryer sheets. They leave a film on the lint filter that cuts airflow. If you use them, scrub the filter with a toothbrush once a month.

An annotated example

What to do next

Clean your dryer's lint filter after every load, whatever kind of dryer it is. If you use dryer sheets, scrub the filter with a toothbrush once a month. Dryer fire safety checklist covers the vent and the rest of dryer safety.