When used to describe a furnace, the term variable speed refers to the indoor blower motor or fan on a high-efficiency system. This allows the blower motor to speed up and slow down gradually to eliminate the blast of cold air often felt when a furnace first comes on for heating. Most brands use a timer to control this operation. When paired with the Carrier Infinity Control, the variable speed motor becomes more independent and will regulate the fan speed based on room temperature to provide your home with warm air circulating throughout your home to help eliminate hot and colds spots during the heating season. During the cooling season, when paired with the Carrier Infinity Control, the blower motor will optimize its speed to provide quicker cooling at higher room temperatures and more gradual cooling once the room is closer to temperature. This results in improved dehumidification and a higher level of comfort in your home. These motors are very energy efficient and often save over $100.00 per season in energy costs. A standard gas furnace offers a multi-speed blower motor or fan and can be set for individual speeds. One speed for heating and another for cooling and they are not adjustable based on temperature or humidity.