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I think the airconditioning takes a big slice of the efficiency. But I'm no engineer either.




If I remember correctly, a typical rotary A/C compressor uses about 1.4 hp. Older piston style compressors like York brand compressors used significantly more.

Another twist is that many newer compressors are variable displacement and can vary the amount of power needed to run based upon the cooling load, so they're more efficient when you don't need as much cool air. Older compressors would cycle on and off using their clutch as more high side pressure was needed for the A/C.