The short answer
Below roughly 3 HP, rotary compressors usually win on cost. Above that, scroll compressors win on efficiency, noise and service life. The overlap zone between 2 HP and 3 HP is where your duty cycle should decide.
How each design works
A rotary compressor uses a rolling piston inside a cylinder to compress refrigerant with one continuous motion. A scroll compressor traps refrigerant between two interleaving spirals and squeezes it toward the centre. Fewer moving parts in the scroll design generally means less vibration and fewer wear points.
Efficiency and operating cost
Scroll compressors hold higher volumetric efficiency, especially under part-load conditions where systems cycle frequently. In a commercial space that runs 10 hours a day, the efficiency difference pays back the extra purchase price over a season or two.
Noise and vibration
If the outdoor unit sits next to a bedroom or a hotel balcony, scroll is the safer choice. Rotary units are quiet at low speed but can transmit more vibration through the copper lines at high load.
Replacement and service reality
Rotary replacements are cheaper and more widely stocked in residential markets; scroll replacements cost more but are standard practice in commercial service. Always check rotation direction on three-phase scroll units before startup.
Decision checklist
Capacity below 2 HP with budget pressure → rotary. Capacity above 3 HP, long running hours or noise-sensitive location → scroll. Anything in between → ask us for models from both families and compare total cost over the service life.