How to use the compressed air leak cost calculator
Compressed air is the most expensive utility in most plants, and a poorly maintained system commonly loses 20 to 30% of its output to leaks. Every cubic foot that escapes has to be made again by the compressor, so leakage converts directly into kilowatt-hours. This tool solves the choked orifice equation for the leak flow at your supply pressure, then applies compressor specific power to give the wasted kW, annual kWh and annual dollars.
Mass flow is calculated as discharge coefficient x orifice area x absolute pressure x 0.002362, then divided by the standard air density of 0.0752 lb/ft3 (1.204 kg/m3) to give free air in SCFM. The discharge coefficient choices follow the note in the DOE Compressed Air Challenge leak tables: 0.61 for a sharp-edged hole, 0.97 for a well-rounded orifice and 1.00 for the theoretical value the published table uses. Selecting 1.00 reproduces that table, for example 6.5 CFM through a 1/16 in hole at 100 psig.
Specific power for a 100 psig lubricated screw compressor is typically 18 to 22 kW per 100 CFM at the motor input. In practice, find leaks with an ultrasonic detector during a quiet shift and pair the repairs with pressure optimization, since each 2 psi of header pressure reduction saves roughly 1% of compressor energy.
Frequently asked questions
Real leaks are irregular gaps that cannot be measured directly. Run a no-load or pump-up test to get total system leakage first, then use this tool to back into an equivalent hole size for comparison.
Yes. Below an absolute pressure ratio of about 1.9 the flow is no longer sonic, so this equation does not apply. Inputs under 15 psig are blocked, and low pressure systems need the subsonic orifice equation instead.