Electric dryers that operate on 120 volts dry clothes using less power than typical electric dryers, which use 240 volts. These dryers are generally used in small homes and in places where electrical service is limited.
It is possible to draw the same wattage from a 120-volt outlet, but doing so draws more amperage. The dryer might draw more power than the main electrical line can supply. As a result, 120-volt dryers are typically much smaller than their 240-volt counterparts to account for this power difference. Small dryers are typically less efficient than larger dryers, so 120-volt dryers are generally only used by people who have no other options.