A modular blower installs in the home and connects to the ductwork to circulate air through the home. A cased evaporator coil can be mounted on the modular blower if central air conditioning (or a heat pump) will be installed. Also, electric heater coils can be easily installed in the modular blower to provide electric heat, making the modular blower an electric furnace. The modular blower is completely preassembled, and consists primarily of a multi-speed or variable-speed fan and electrical controls. It can be installed either vertically, horizontally or in a down-flow position (if using an evaporator coil in the horizonal position, select a horizontal evaporator coil). The difference between a modular blower and an air handler is that a modular blower does not contain a pre-installed evaporator coil (can be added as an external accessory), whereas an air handler does. Also, a modular blower with an external cased evaporator coil usually has a slightly higher efficiency rating (SEER) when used in an air conditioning or heat pump system than when an air handler is used (check heat pump or condenser specification sheets for details).