Electric Dryers

• To heat the air that a dryer pulls in from the outside, electric dryers use electric heating elements. Ambient air drawn in from the outside passes through electric coils that heat the air before it's distributed by an electric fan throughout the dryer. The electricity needed to power the coils as well as the other electric components in the dryer, such as the thermostat for auto-dry settings and electric buzzers that sound when a drying cycle is complete, necessitate the use of a 240-volt electrical outlet, twice the voltage of most standard household electrical outlets.
  
  

Gas Dryers

• Gas dryers use a natural gas burner to heat the air drawn in from the outside, not unlike a gas burner on the cooktop of a stove. Gas dryers therefore require a natural gas hookup as well as a nearby electrical outlet to power the other electrical functions of the dryer that are separate from the heating process. Because of the health and safety concerns that can result from the buildup of natural gas particulates in the air, gas dryers also require a means for venting gas fumes out of the room, just as gas stove cooktops need ventilation systems above them to remove harmful gas fumes.
  
  

Microwave Clothes Dryers

• New dryer technologies, though many are still in their infant stages, may provide more efficient and less hazardous and costly methods for heating the air used to dry clothes. The technology used isn't unlike that in a microwave oven; microwave particles are dispersed among the clothes via an electric fan and heat the water molecules on wet clothes to the point of evaporation, just like fan-dispersed microwaves accelerate the water molecules in food to heat and cook it. Microwave clothes dryers are still relatively obscure and difficult to procure due to prohibitive cost and safety concerns, but several manufacturers are still investing in the future of microwave clothes dryers.
  
  

Other Dryer Types

• Other types of dryers that use alternative methods for heating air to dry clothes are more readily available. Condenser dryers draw air in from the outside and heat it just as a gas or electric dryer, but condenser dryers capture the moisture that's removed from clothes, condense the moisture using a heat exchanger, discard the liquid, and recycle the air from the condensate to be reused in the same cycle, thus eliminating the need for a dryer vent to remove hot air. Heat pump dryers use the same concept but through the use of a heat pump rather than a heat exchanger. Still other types of dryers in various stages of development use solar energy, convection, and steam compression to heat and reheat the air used to dry clothes.