Condenser (Single stage)
A condenser unit is used to cool down and condense incoming refrigerant vapor into liquid, a compressor to raise the pressure of the refrigerant and move it along, and a fan for blowing outside air through the heat exchanger section to cool the refrigerant inside.
Condenser (two stage or variable Speed)
Two-stage cooling refers to the type of compressor that’s in the outside condensing unit. This feature allows for two levels of operation depending on your cooling needs — full capacity on hot summer days or part capacity for milder days.
While these units are more expensive in comparison to their single stage counterpart, having a 2 stage set up can ultimately save you more money on your electric bill.