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Compressed air cost and leaks

Enter the compressor, hours and electricity price to find what the air costs, how much goes to leaks and unloaded running, and what a leak program and lower pressure are worth.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

Preliminary estimate
Compressor and system
Leaks

Usual test: with production stopped, compressor loaded time divided by total time.

Proposed improvements
Economic analysis
—Annual energy cost of compressed air
—

Where the energy goes

Yearly energy split into useful demand, leaks and unloaded running, today and with the improvements.

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Annual cost of a single hole

Each line is a hole diameter; choked orifice flow, at the electricity price and hours entered.

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Next step

Take this page’s results to another calculator with the fields already filled in.

Distribution pressure drop →Receiver volume →

Project payback

Cash flow of the improvement: investment in year 0 and annual savings escalated at the rate entered, discounted at the MARR.

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The report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. In the print dialog, choose Save as PDF.

Method, assumptions and references

Equations used

Annual energy = P × (loaded share) × hours + P × (unloaded fraction) × (1 − loaded share) × hours
Specific power = P ÷ FAD; cost of air = annual cost ÷ annual volume produced
Hole (choked flow, ideal gas): ṁ = Cd · A · p1 · √(γ ÷ (R·T)) · (2 ÷ (γ+1))^((γ+1) ÷ (2(γ−1))), with γ = 1.4
Compression work (adiabatic, n stages): W ∝ n · [(p2 ÷ p1)^((γ−1) ÷ (γ·n)) − 1]
Leak flow after pressure reduction ∝ absolute pressure (choked flow)

Assumptions and limits

  • Constant full-load power and unloaded power as a fraction of it; variable speed compressors may behave differently.
  • Inlet air at 20 °C (68 °F) and 14.7 psia; leaks treated as orifices with the discharge coefficient entered.
  • Pressure reduction assumes all end uses are still served; check the worst point of the network first.
  • Validation: with a discharge coefficient of 1, the calculated flow matches the DOE leak table (1/8" hole at 100 psig ≈ 26 cfm); the 0.65 default represents sharp-edged holes.
  • Artificial demand (unregulated use that grows with pressure) not included: actual savings tend to be larger.

Standards and technical documents

  • ISO 11011:2013: Compressed air — Energy efficiency — Assessment
  • ISO 1217:2009: Displacement compressors — Acceptance tests (FAD and specific energy)
  • ISO 8573-1:2010: Compressed air — Contaminants and purity classes
  • U.S. DOE, Improving Compressed Air System Performance: A Sourcebook for Industry (3rd ed.); Compressed Air Challenge, Best Practices for Compressed Air Systems
  • Escoamento compressível em orifício: Shapiro, The Dynamics and Thermodynamics of Compressible Fluid Flow / choked orifice flow

U.S. regulations

  • DOE 10 CFR Part 431, Subpart T: energy conservation standards for air compressors (rotary, 10 to 200 hp)
  • OSHA 29 CFR 1910.169: air receivers (ASME construction, drains, safety valves) and 1910.242(b): compressed air for cleaning under 30 psi
  • ASME BPVC Section VIII, Division 1: construction of air receivers

Frequently asked questions

How much does a compressed air leak cost?

A 1/8" hole at 100 psig loses about 17 cfm (discharge coefficient 0.65). At 17.7 kW/100 cfm, 6,000 h a year and $0.09/kWh, it costs roughly $1,600 per year. The chart shows cost by hole size and pressure.

How much does a 2 psi reduction save?

Compression work drops about 1% per 2 psi around 100 psig, and leaks shrink too because flow through a hole is proportional to absolute pressure.

How do I measure leakage?

With production stopped and the system pressurized, time the compressor’s loaded periods. Loaded time divided by total time is the share of output lost to leaks (DOE and ISO 11011 method).