By Marcus Lindqvist · Updated September 27, 2026 · 6 min read
Short answer
Scroll compressors are compact, quiet and efficient at small to mid capacities and are usually sealed units that are replaced rather than overhauled. Screw compressors cover mid to very large capacities, handle high pressure ratios and varying loads with slide valves or variable speed, and are built to be inspected and overhauled. The right choice depends mainly on capacity, duty and who will maintain the machine.
Scroll and screw compressors both compress refrigerant continuously rather than in strokes, which makes them smoother than reciprocating machines. The difference is scale and construction. Scroll compressors dominate small and mid-size capacities in a sealed housing. Screw compressors take over as capacity and duty grow, and they are designed to be opened, inspected and overhauled. For the full range of options, see our guide to refrigeration compressor types.
How does each type compress refrigerant?
Scroll. Two spiral elements sit one inside the other. One stays fixed and the other orbits without rotating. The moving pockets of gas shrink toward the center and the pressure rises. There are no suction valves, only a discharge port, and few moving parts.
Screw. Two helical rotors, one male and one female, mesh inside a housing. Gas enters at one end, is trapped between the lobes and is squeezed as the rotors turn. Oil is injected to seal, cool and lubricate. A separator removes the oil from the discharge gas. The details are in how a screw compressor works.
How do they compare?
| Factor | Scroll | Screw |
|---|---|---|
| Typical capacity per compressor | small to mid, commonly up to about 15 to 20 tons, larger in tandem | mid to very large, from roughly 20 tons to well over 1,000 |
| Construction | usually hermetic, welded shell | semi-hermetic or open drive |
| Capacity control | on/off, tandem staging, digital or variable speed | slide valve or variable speed drive |
| Part-load efficiency | good with staging or variable speed | good with slide valve and variable speed |
| Pressure ratio tolerance | moderate | high |
| Noise and vibration | low | moderate, usually acceptable |
| Oil system | oil sump inside the shell | external oil separator, cooler and filter |
| Serviceability | replaced as a unit | inspected, rebuilt or overhauled |
| Typical uses | rooftop units, small chillers, heat pumps, light commercial refrigeration | industrial refrigeration, process and mid to large chillers |
Capacity ranges overlap and vary by manufacturer and refrigerant. Treat the table as a starting point and use the manufacturer’s selection data.
Which one is more efficient?
Neither always wins. A scroll compressor operating inside its design range is very efficient, partly because it has no suction valves and little re-expansion loss. A screw compressor loses some efficiency at deep part load if it relies only on a slide valve, but variable speed drives and multiple machines narrow that gap. At large capacities a screw machine’s efficiency, high-pressure-ratio capability and low-temperature performance are usually decisive.
Compare at your actual conditions: suction and discharge temperatures, load profile and refrigerant. Efficiency ratings such as kW per ton should be read against the same rating conditions, as we explain in how a chiller works.
Which one is easier to maintain?
Scroll compressors need little routine attention, but when one fails the usual remedy is replacement because the shell is welded and the internal parts are not field-serviceable. Scroll units in a tandem or multi-compressor chiller give redundancy: one can fail while others carry the load.
Screw compressors have more support equipment, namely the oil separator, cooler and filters, and they need oil analysis and vibration monitoring. In return, the compressor itself can be inspected and overhauled: bearings, shaft seals and rotor clearances are replaceable. That is why large plants often prefer them. For wear indicators, see five signs a compressor is wearing out and what oil analysis tells you.
What are typical applications?
- Scroll: packaged rooftop units, air-cooled and water-cooled chillers up to a few hundred tons using multiple compressors, heat pumps, display cases and small walk-in systems.
- Screw: process chillers, cold storage and food plant refrigeration, data center chillers, ammonia plants and large air-cooled or water-cooled chillers. See industrial chillers: types and how to choose.
How should you choose?
- Start with capacity. Under roughly 20 tons per circuit, scroll is common. Above a few hundred tons per machine, screw or centrifugal takes over.
- Look at the load profile. A steady, large load suits screw. A small, cyclic load suits scroll staging.
- Check refrigerant and temperature. Low suction temperatures and high pressure ratios favor screw.
- Think about who will service it. A site with trained staff may prefer an overhaulable machine. A small site may value a sealed unit that is simply replaced.
- Plan for redundancy. Several scrolls in one chiller or several machines in one plant reduce single-point failure risk.
- Check future refrigerant approval. Confirm that the model is approved for lower-GWP options; see A2L refrigerants explained.
Frequently asked questions
Can a scroll compressor be rebuilt?
Sealed scroll compressors are normally replaced. Some larger or special-purpose scrolls can be repaired by the manufacturer, but that is the exception.
Are screw compressors always oil-flooded?
In refrigeration, nearly all are oil-injected because the oil seals and cools the compressor. Oil-free designs exist in air compression but are rare in refrigeration.
Which is quieter?
Scroll compressors are generally quieter and smoother. Screw compressors are acceptable in most plants, but plant rooms often need sound treatment.
SpecServis engineers in Ukraine have worked with both types in industrial refrigeration and chillers. We are planning to enter the Central Texas market and are looking for technicians, partners and a company to buy. See our open positions or partnership options.
