VSD vs Fixed-Speed Screw Compressor energy and cost savings calculator based on CAGI and ISO 1217 compliant formulas.
Compressor nameplate data
kW
m³/min
bar(g)
Specific power (from CAGI data sheet)
kW/m³/min — from CAGI data sheet at rated pressure
kW/m³/min — from CAGI data sheet at part-load operating point
Operating profile
This is the most critical variable — measure it from compressor controller logs or a data logger. Do not guess.
h/year (max 8,760)
₹/kWh
% — CAGI typical: 25–35%. Use 30% if unknown.
Summary
Fixed-speed avg. power
—
kW
VSD avg. power
—
kW
Power saved
—
kW average
Fixed-speed annual energy
—
kWh/year
VSD annual energy
—
kWh/year
Annual cost saving
—
₹/year
Savings analysis
Side-by-side comparison
| Metric | Fixed-speed | VSD | Delta |
|---|---|---|---|
| Avg. power (kW) | — | — | — |
| Annual energy (kWh) | — | — | — |
| Annual energy cost (₹) | — | — | — |
| Specific power (kW/m³/min) | — | — | — |
Step-by-step calculation trace
Engineering disclaimer: These estimates are based on CAGI data sheet methodology and ISO 1217:2009 Annex C principles for specific energy performance comparison. Results are indicative only and depend entirely on the accuracy of the specific power values entered from manufacturers’ CAGI data sheets and the measured load profile. Actual field savings can vary due to system pressure fluctuations, inlet air conditions, installation losses, motor efficiency variations, and drive losses. An on-site energy audit with data-logged load profiles is required for investment-grade figures. VSD savings below 15% may not justify the capital premium at low load factors (<40%). This tool makes no warranty of savings achievement.