Which of the following types of air conditioning compressors is most energy efficient?

• A. Reciprocating
• B. Centrifugal
• C. Screw
• D. Scroll

Answer: (B)

In air conditioning, how effectively a compressor uses electricity to move refrigerant is the key to energy efficiency. Centrifugal compressors are most efficient for large-capacity systems because they use dynamic compression with very few moving parts, which minimizes mechanical losses. The impeller accelerates refrigerant and converts that kinetic energy into pressure, so for the same cooling load they typically require less shaft power than positive-displacement types. They also partner well with variable-speed drives, allowing the compressor to match load smoothly and avoid energy-wasting starts, stops, or throttling losses that other types experience at partial loads. While other compressor types—like reciprocating, screw, or scroll—can be efficient in certain ranges, their higher friction, pulsations, or leakage losses across a wide load range generally result in lower overall energy efficiency.