The compressor is the heart of any refrigeration or HVAC system. It pressurizes the refrigerant gas, raising its temperature and pressure so it can release heat in the condenser. The compressor is typically located in the outdoor unit of split systems.
There are several types of compressors used in residential HVAC: reciprocating (piston-based, older technology), scroll (most common in modern residential equipment — quieter, more efficient, fewer moving parts), rotary (used in smaller units and mini-splits), and variable-speed/inverter-driven compressors (the most efficient, constantly adjusting output to match demand).
Compressor failure is the most expensive HVAC repair, often costing $1,500-2,800 or more. Regular maintenance including keeping refrigerant levels correct, changing filters, and maintaining coil cleanliness extends compressor life. Most compressors carry a 5-10 year manufacturer warranty.