Air conditioners are available with single-stage, two-stage, and variable speed compressors. A single-speed compressor has only On and Off settings, so it’s always running at one constant speed or not at all. Two-stage compressors have two speeds, meaning they can operate at a lower or higher setting when they're running. These are quieter, more efficient, and better at keeping temperatures even. Variable-speed compressors have many speeds and can make incremental adjustments to the speed to increase efficiency, reduce noise, and keep every corner of your house at the same temperature all the time.