Definition
A compressor is the motor-driven pump in an air conditioner or heat pump that squeezes low-pressure refrigerant vapor into hot, high-pressure vapor, keeping refrigerant circulating through the whole system. It sits in the outdoor unit and comes in single-stage, two-stage and variable-speed designs. It is usually the most expensive single component to replace.
Why it matters to you
In a heating-dominant climate like SW Washington's, a heat pump compressor works through the long, damp winter as well as summer, so its run hours add up faster than those of an AC-only compressor. On older systems built for R-22, whose production and import ended January 1, 2020, a compressor failure usually starts the repair-or-replace conversation.
Practical guidance
Warning signs include an outdoor unit that hums but will not start, repeated breaker trips or warm air in cooling mode; switch the system off at the thermostat and call a licensed technician. Ask for the diagnosis in writing, including refrigerant type and system age, and consider a second opinion before approving a compressor replacement.
About this definition
Written by the Home Energy Group team — a family-owned HVAC company celebrating 25 years of comfort & care across SW Washington and the Portland metro, licensed in Washington (WA LIC# HOMEEGI003J7) and Oregon (OR CCB# 184255). Definitions inform; an on-site diagnosis decides.
