The Lennox HS25 is a high efficiency air conditioner equipped with a scroll compressor. The scroll compressor contributes to the high efficiency in the way it compresses the refrigerant. 

The Lennox G21Q series Pulse 21 furnace has no gas burners, no standing pilot, fewer parts to maintain, and has built-in safety features that automatically monitor gas flow and ignition.  The pulse combustion process is the only process that is self-sustaining.  It draws in outdoor air and vents the exhaust without the use of an auxiliary blower assembly.