Formula
kW/100 CFM = (package kW ÷ delivered CFM) × 100 · benchmark corrected ≈ 1% per 2 psiSpecific power
19.5kW / 100 CFM
82 kW input · 4.2 CFM per hp
Typical for this class
19.7kW/100
Rotary screw · 100–200 hp
Best in class
17.9kW/100
Current CAGI sheet leaders
Verdict
Within benchmark — -1% vs typical
Efficiency is in line with a healthy package of this size at this pressure.
+9% versus a best-in-class replacement.
Annual energy
- Current spend at this operating point
- $59,040
- Savings if brought back to typical
- $0
- Savings against a best-in-class unit
- $5,062
Use the same flow measurement for both sides of the comparison. A pump-up test or a real flow meter is worth the trip — nameplate CFM on a 12-year-old airend is optimistic by 5–15%.
CAGI reference — kW per 100 CFM at 100 psig
| Package | Size | Typical | Best |
|---|---|---|---|
| Rotary screw — lubricated, fixed speed | 5–15 hp | 24.5 | 22.0 |
| Rotary screw — lubricated, fixed speed | 20–30 hp | 22.0 | 20.0 |
| Rotary screw — lubricated, fixed speed | 40–75 hp | 20.5 | 18.5 |
| Rotary screw — lubricated, fixed speed | 100–200 hp | 18.8 | 17.0 |
| Rotary screw — lubricated, fixed speed | 250 hp and up | 18.0 | 16.3 |
| Rotary screw — lubricated, variable speed | 10–30 hp | 22.5 | 20.5 |
| Rotary screw — lubricated, variable speed | 40–75 hp | 20.8 | 18.8 |
| Rotary screw — lubricated, variable speed | 100–200 hp | 19.2 | 17.3 |
| Rotary screw — lubricated, variable speed | 250 hp and up | 18.4 | 16.6 |
| Rotary screw — oil-free, two stage | 50–100 hp | 22.5 | 20.5 |
| Rotary screw — oil-free, two stage | 125–300 hp | 20.5 | 18.6 |
| Rotary screw — oil-free, two stage | 350 hp and up | 19.6 | 17.8 |
| Reciprocating — two stage, lubricated | 5–30 hp | 19.5 | 17.5 |
| Reciprocating — two stage, lubricated | 40 hp and up | 18.5 | 16.5 |
| Reciprocating — single stage | all sizes | 25.0 | 22.5 |
| Scroll — oil-free | all sizes | 27.0 | 24.0 |
| Centrifugal — multistage | 300 hp and up | 17.5 | 15.8 |
Benchmarks are planning-grade averages of published CAGI performance data. For a quotable audit, pull the CAGI data sheet for the exact model and control scheme, and log kW and CFM simultaneously over a full production shift rather than at a single instant.
How to use this calculator
Convert measured kW and CFM into specific power (kW per 100 CFM) and compare it with published CAGI performance for the same class of machine.
- Measure true input kW at the compressor disconnect with a power meter, not a clamp-on amp reading alone.
- Enter measured flow in CFM and the discharge pressure the machine was making during the test.
- Select the package type — lubricated screw, VSD screw, oil-free or reciprocating — and the horsepower class.
- Read specific power in kW/100 CFM and compare it against the benchmark band shown for that class.
- Use the annual energy rows to convert any shortfall into dollars per year at your utility rate.
Frequently asked questions
- What is a good specific power for a rotary screw compressor?
- A well-maintained lubricated rotary screw in the 100–200 HP range typically runs about 17–19 kW per 100 CFM at 100 psig. Smaller packages run higher, around 20–24 kW/100 CFM, and large two-stage machines can reach 15–16 kW/100 CFM.
- Why is my measured specific power worse than the CAGI sheet?
- CAGI data is a full-load bare-package figure at a stated pressure. Real installations lose ground to part-load operation, a dirty separator or inlet filter, higher discharge pressure than the rating point, a hot inlet, and dryer or piping losses included in the metered kW.
- How much does discharge pressure affect power?
- Roughly 1% of input power for every 2 psi of discharge pressure on a positive-displacement compressor. Dropping a header from 120 psig to 105 psig is worth about 7–8% on the compressor alone, plus the artificial-demand savings downstream.