Why do you need an air handler?
A home comfort system has two parts: an outdoor unit, such as an air conditioner or heat pump, and an indoor unit. The air handler is the indoor unit that circulates cool air through your home in the summer and warm air in the winter. The indoor and outdoor units are designed to work together. And, when the air handler is properly matched with a heat pump or air conditioner, the result is maximum efficiency and extended system life.

Some companies like York® offer air handlers that use ECM technology as opposed to typical blower motors. This technology can increase SEER efficiency ratings by up to 1.5 points. And variable speed operation also allows for quiet unit operation, eliminating noisy starts and stops.