Considered the heart of air conditioning and heat pump systems, the compressor pressurizes and pumps refrigerant back and forth from the condensing unit to the evaporator, which in turn serves to adjust the temperature in interior spaces. The refrigerant works by absorbing and releasing heat as it travels between the two units. The compressor uses pressure to help change the composition of the refrigerant from a gas to a liquid and accelerate the removal of heat trapped in the refrigerant. The entire process significantly enhances the natural tendency of heat’s movement to colder spaces, with blowers and fans pushing the cooled or heated air accordingly. The difference between an A/C and heat pump compressor essentially depends upon the direction of the circulated refrigerant. Both types come with single-stage or two-stage variations, with the latter offering high- or low-level operations to account for milder temperature variations. That said, most HVAC systems utilize single-stage systems.