Improper duct sizing can significantly impact the performance of a central heating and cooling system. Overly large ducts can require larger fans or just work harder to push conditioned air through the duct system. Ducts that are too small, too long, or too winding may make the fan work harder to overcome greater air pressure. Improper sizing can cause excessive energy use, premature wear-and-tear on the fan, and comfort issues. Ducts properly designed and sized by a comfort system professional will take into account house geometry, climate, and techniques to make the duct layout more efficient.