As the evaporator picks up heat from your house, the heat is transferred to the condensing unit outside via refrigerant where it is condensed and cooled. Critical to this cooling process is a working condenser fan and clean coils. Dirty coils reduce efficiency and very dirty coils can render a unit nearly inoperable. Methods vary when it comes to cleaning coils. The old-style louvered Rheem coils needed to have the fan removed and the cols sprayed from the inside out to dislodge debris from the coils and then the rinse the louvers. Inspect and repeat if necessary. A lot of the newer louvered condensers have easily removable panels to make cleaning easier. After removing the panels on these units, one can simple rinse the debris from top to bottom without worrying too much about driving debris into the coils. Efficiency varies widely even on the same unit depending on how clean the coils are-lb