The 6 types · side-by-side

Distributor-facing reading. Each row gives best-for, key trade-off, capacity, price band, and how many of SPC's tier slots carry an option at that product type.

Product type

Best for

Key trade-off

Typical capacity

Price band

Brands SPC carries

Rotary Screw — Fixed-Speed Continuous plant duty · steady load · ~4 CFM/HP

The industrial workhorse.Production-line air, automotive plants, plastics, woodworking, food packaging (non-direct-contact). Any operation that runs air all day at a roughly steady draw within ~30% of rated capacity. The default compressor for industrial duty when demand stays close to rated.

Wastes energy on swinging demandAn unloaded motor still draws 25-40% of full-load power without producing air. If demand swings wider than ~30% of rated, the unloaded cycles burn $4-8K/year of electricity making nothing — that's the case for a VFD, not fixed-speed.

5 – 500+ HP · 20 – 2,000+ CFM
belt-drive (stocked) · direct-drive (lead-time)

$$ – $$$

5 / 5 · deep

Rotary Screw — VFD Variable demand · 25-50% energy savings · single-setpoint pressure

Multi-shift and batch plants.Any facility where air demand swings hard across the day — multi-shift manufacturing, batch chemical, auto assembly, food packaging, plastics with cycling presses. Holds pressure on a single setpoint instead of drifting across a band, which is a second energy dividend on top of matched-demand savings.

Premium upfront · electronics to failRoughly $2-5K premium over fixed-speed, repaid in 1-3 years on energy where demand actually swings. Drive cabinet derates above 104°F ambient. Multi-VFD plants need harmonic mitigation (line reactor or active filter) to stay inside IEEE 519.

5 – 450+ HP · 20 – 1,800+ CFM
induction motor · permanent-magnet (premium tier)

$$ – $$$

3 / 5 · solid

Reciprocating Intermittent shop duty · 60-70% loaded · field-rebuildable

Shops, body work, small fabrication.Two-bay auto shops, body shops, small machine shops, agricultural buildings, residential garages, equipment-rental yards. The entry point of the category — lowest upfront cost, simplest mechanism, common-parts rebuild. Two-stage cast-iron Quincy QR-25 class is a 15-year machine when the duty cycle stays honest.

Not continuous duty · loudCast-iron pump capped at ~60-70% loaded time per hour; run harder and it overheats, the rings glaze, valves cook, and rebuild interval collapses. 80-90 dB versus rotary screw's 60-75. If the customer's real duty is continuous, recip is the wrong tool.

Fractional HP – 30+ HP · 1 – 120+ CFM
single-stage to ~175 PSI · two-stage to ~200 PSI

$ – $$

5 / 5 · deep

Oil-Free ISO 8573-1 Class 0 · screw / tooth / scroll

Food, pharma, medical, electronics, fine finishing.Any application where compressed air touches product, package, or process gas directly. Pharma fill-finish, food packaging blowoff, semiconductor wafer handling, dental and lab air, automotive paint, breathing-air supply. The architectural answer to "no oil allowed" — certified Class 0, not "low oil."

2-3× the cost · still needs treatmentRoughly 2-3× the price of an equivalent oil-lubricated unit; ~5-10% lower full-load efficiency from tighter tolerances and extra cooling. Oil-free at the source does NOT dry the air or remove particulate — downstream dryer + filtration is still the full stack.

1.5 – 500+ HP · 4 – 2,000+ CFM
scroll · rotary tooth · two-stage screw

$$$

2 / 5 · Atlas Copco + ELGi

Portable / Contractor Wheeled or skid · 120V / 240V / generator / off-grid

Take the air source to the work.Framing and roofing crews, mobile auto service, body-shop frame work, agricultural service, disaster response, equipment-rental fleets. Reciprocating mechanics on a wheeled or skid frame — sized small (fractional HP to ~10 HP) for the air budget of one crew.

Off-grid needs the dryer pairingMost distributors quote the compressor and forget the dry-air problem. No-power sites need a deliquescent dryer paired with the compressor — passive vessel, dry-desiccant tablets, no electricity. The off-grid stack is moving compressor + passive dryer; ignore that and the customer can't run paint or finish work on the job.

Fractional HP – 10 HP · 2 – 35 CFM
hand-carry · wheeled · skid (forklift)

$ – $$

1 / 5 · Castair only

Duplex / Triplex System Two or three pumps · shared receiver · lead-lag staging

Uptime is the priority.Hospitals on NFPA 99 medical air (code-required redundancy), continuous- process chemical and semiconductor, automotive paint and finishing on JIT contracts, food and beverage packaging, plants outgrowing their original single compressor. When a day's air outage costs more than the second pump.

Size for one-pump-out, not nameplateDuplex with both pumps at 100% of demand is not redundant — it's just two compressors. Quote duplex sized so a single pump covers full demand (or triplex so two pumps do). Shared receiver goes against COMBINED output (4-6 gal/CFM combined); undersized tank short-cycles the lead regardless of how clever the stager is.

10 – 60+ combined HP · 35 – 200+ combined CFM
lead-lag staging · alternating-lead wear balancing

$$ – $$$

2 / 5 · Atlas Copco + Castair

Reading the brand bench column — the bar shows how many of SPC's tier slots (Industry Leader · Emerging · Economical · adjacent) carry an option at that product type. A deep bench means a price-driven and a spec-driven option both close cleanly; a narrow bench means the available brands map closely to the technical requirements and the comparison stops being a tier choice. Generation has SPC's deepest brand bench in the whole system on the reciprocating and fixed-speed-screw rows; the bench narrows deliberately on oil-free (Class 0 architecture has real engineering content that economical-tier makers don't deliver reliably) and on portable (most contractor portables in the field are Castair-class regardless of badge).