An air handler installs in the home and connects to the ductwork to provide cooling or electric heat (optional) indoors. The air handler is completely preassembled, and consists primarily of a multi-speed or variable-speed fan, built-in evaporator coil, and electrical controls. Depending on the model, they can be installed vertically, horizontally or in a downflow orientation. If winter heating is needed, an optional electric heater coil can be easily installed into the air handler.