Variable speed air handlers are more efficient. Since variable speed units typically operate at lower speeds than constant speed air handlers, they use less energy, and lower your heating and cooling bills. In fact, a typical variable speed unit uses 80 percent less electricity to run the fan than a similar constant speed blower.
Variable speed air handlers are quieter than constant speed units for two reasons: First, variable speed units don't cycle off and on continually, as with constant speed air handlers; this reducing both duct and fan noise. Second, the lower fan speeds of the variable speed units are inherently quieter than the higher speeds used in constant speed air handlers.
Variable speed air handlers provide more uniform heating and cooling. Variable speed units continually circulate the air in your home. This prevents uncomfortable hot spots and cold spots.
When used for air conditioning, variable speed air handlers are much more efficient at removing humidity from the air. This greatly increases comfort in summer months.
Variable speed systems can produce cleaner air. Because variable speed units constantly circulate and filter the air, the air in your home is cleaner.