The LSU121HSV3 is a singlezone condenser and requires the LG LSN121HSV3 air handler to operate. The LSU121HSV3 is the outdoor unit only, indoor units are sold separately and are required to run this model. The LG LSU121HSV3 is a condenser unit for a ductless split system air conditioning system. It features 11,200 BTU cooling and 13,300 BTU heating capacity and connects to the indoor air condenser through tiny, easy to install refrigerant lines and tubes. LG's ductless systems function much like a central air system, but without the hassle and unattractiveness of invasive ductwork. This LG air conditioning system uses environmentally friendly R410A refrigerant for cooling and an incredibly effective heat pump inverter for warming the single zone where it is installed. The heat pump of this leading LG unit uses compressors with AC to DC inverter technology, which have variable speeds. This allows the continuously matching of the heating and cooling load and avoids the on/off cycling of conventional central heating systems and electric resistance, which often have high energy usage. This model has an EER rating of 12. 5 and a SEER rating of 20, making it a truly energy efficient option.