How to use this calculator
- Choose leak basis. Use measured leak flow from a survey or estimate flow from equivalent orifice diameter.
- Enter pressure and orifice details. For orifice mode, enter upstream pressure, downstream pressure, temperature and discharge coefficient.
- Enter compressor energy data. Use compressor specific power in kW per SCFM at the operating pressure.
- Enter operating cost assumptions. Set electricity rate, annual pressurized hours, leak duty factor and optional repair cost.
- Review cost and payback. Use annual cost, monthly cost and repair payback to prioritize leak repairs.
How it works
This compressed air leak cost calculator supports two flow paths. If you already have a leak survey, measured-flow mode uses the entered free-air leak rate directly. If you only have an equivalent hole size, orifice mode estimates dry-air flow through a round leak using compressible ideal-gas flow.
For a choked leak, the mass flow is proportional to upstream absolute pressure and orifice area:
mdot = Cd * A * P1 * sqrt(gamma / (R*T)) * (2/(gamma+1))^((gamma+1)/(2*(gamma-1)))
The mass flow is converted back to equivalent free-air flow at atmospheric pressure. Cost then uses the entered compressor specific power:
P_waste = Q_leak,SCFM * specific power
cost_year = P_waste * hours_year * duty * electricity rate
Worked example
Verified against the live calculator
A 1.5 mm equivalent leak at about 100 psi gauge
to atmosphere is roughly 4.9 SCFM with the default
discharge coefficient. At 0.18 kW/SCFM, that is about
0.89 kW of compressor input. If the system is pressurized
all year at $0.12/kWh, the leak costs about
$930 per year.
Frequently asked questions
How do you calculate the cost of a compressed air leak?
Start with leak flow in SCFM, multiply by compressor specific power in kW/SCFM to estimate wasted input power, then multiply by operating hours and electricity rate: cost = SCFM x specific power x hours x $/kWh.
What if I only know the leak hole size?
Use orifice mode. It estimates dry-air flow from equivalent round orifice diameter, upstream pressure, downstream pressure, air temperature and discharge coefficient. At typical plant pressures leaking to atmosphere, the flow is often choked.
What is compressor specific power?
Specific power is compressor package input kW divided by delivered SCFM at the operating pressure and control mode. Use measured data or compressor documentation when possible; the default is only a screening value.
Does this include demand charges or compressor controls?
No. It is a simple energy-cost screen. Sequencing, unload power, VFD turndown, receiver storage, pressure setpoint changes, demand charges and utility tariffs can change the real savings.
Method & assumptions
- Free-air flow is reported as Nl/min or SCFM, not compressed receiver volume.
- Orifice mode assumes dry air, ideal-gas behavior, a round equivalent opening and a user-entered discharge coefficient.
- Cost is based on user-entered compressor specific power, electricity rate, pressurized hours and leak duty factor.
- Does not model compressor trim/unload power, VFD turndown, compressor sequencing, demand charges, pressure-drop savings, heat recovery, repair labor variability or live utility tariffs.
Related compressed-air workflow
Use pneumatic air consumption for cylinder demand, compressed-air receiver sizing for storage, and pneumatic valve Cv for valve pressure-drop screening.