Compressed Air Energy Audit AU: ISO 11011 + NSW Funding

By Byron Raal, CAS Founder-Editor · Last updated 7 June 2026 · About the author

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A compressed air energy audit in Australia follows ISO 11011:2013 methodology: measure supply-side performance (compressor power, specific power, pressure profile), demand-side consumption (flow at branches and end uses), and losses (leaks at 20-30% on typical systems, artificial demand, inappropriate uses). At ~$0.30/kWh AU industrial tariff, electricity is 70-80% of compressor lifetime cost. NSW Energy Savings Scheme funds eligible upgrades. If a grant round can part-fund the work, the audit doubles as application evidence: check the current grants and incentives map first.

How do I run a compressed air energy audit?

Five-step compressed air energy audit method: demand profile, specific power, pressure band, heat recovery, business case (ISO 11011). - by Compressed Air Solutions, licensed CC BY 4.0.

Rule-of-thumb diagram: every 1 bar drop in generation pressure saves about 7% of compressor energy. - by Compressed Air Solutions, licensed CC BY 4.0.

100-square waffle chart showing only about 10-15% of a compressor's energy becomes useful work, the rest lost mainly as heat. — 100-square waffle chart showing only about 10-15% of a compressor’s energy becomes useful work, the rest lost mainly as heat. - by Compressed Air Solutions, licensed CC BY 4.0.

Compressed air energy audits in Australia follow ISO 11011:2013 methodology, which structures the assessment across four areas: demand profiling (logged kWh against measured air flow), specific power benchmarking (kW per L/s FAD against published reference), pressure band analysis (reducing setpoint by 1 bar typically saves 6 to 7 per cent of energy), and heat recovery potential (50 to 80 per cent of compressor electrical input is available as recoverable thermal output).

Why compressed air is the most expensive utility on the plant

Modelled annual compressed air leak cost by Australian manufacturing sector, central case, total 276 million dollars a year; food, beverage and tobacco the largest at 79 million. — Modelled annual compressed air leak cost by sector, central case, total $276M a year. Source: Compressed Air Solutions, CC BY 4.0.

Compressed air burns budget twice: first at the meter, then again through heat loss, leaks, pressure overshoot, inappropriate uses, and fixed-speed part-load waste. That’s why it typically costs seven to ten times the electricity that produced it, measured per unit of useful work delivered at the end-use. The compounded inefficiencies sit in five categories: heat loss at compression (80-90% of input energy), distribution leaks (20-30%), pressure-band overshoot, inappropriate end-uses (open blowing, abandoned drops, oversized regulators), and partial-load efficiency penalties on fixed-speed compressors (per US DOE, Compressed Air Sourcebook audit-baseline guidance).

Page conventions: all pressures are bar gauge (barg) unless otherwise noted. PSI conversions, where shown, are for reference only.

At a typical Australian C&I marginal tariff of approximately $0.30 per kWh for the 2025-26 financial year (actual rates vary by state, retailer, and contract), a 75 kW shaft compressor draws roughly 82 kW total electrical input (per the shaft-vs-total basis below); running 4,000 hours per year at $0.30/kWh, that lands in the order of $98,400 in electricity alone. The audit math is blunt: every percentage point of leak rate on this system is approximately $984 per year of pure waste. A 25% leak rate, common on never-audited sites, represents over $24,000 annually that disappears through unmaintained joints. If the provider doesn’t turn that into a ranked opportunity register, it’s just a walk-through (per US DOE, Compressed Air Systems programme).

The audit pays for itself if it identifies even 10% achievable savings, a hurdle nearly every previously-unaudited site clears. Typical first-audit outcomes recover 20 to 35 per cent of compressed-air electricity spend with payback inside 12 to 24 months. Don’t accept a savings claim that won’t show the data file behind it. For waste-heat opportunities specifically, the heat-recovery ROI calculator quantifies fuel saving and payback period for a compressor retrofit.

Receiver tank sizing: isothermal Boyle’s Law

Receiver tanks buffer short-burst peak demand, and bad receiver maths turns into either nuisance pressure drops or unnecessary steel. Don’t size receivers from catalogue folklore. Sizing them correctly is the single most-misunderstood arithmetic in compressed-air engineering. The valid formula for short-burst (isothermal) demand is:

V_receiver = (Q_peak x t_burst x P_atm) / (P_max − P_min)

Where Q_peak is peak burst flow in L/s FAD, t_burst is burst duration in seconds, P_atm is atmospheric pressure (101.3 kPa absolute), P_max and P_min are the maximum and minimum acceptable tank pressures in absolute kPa.

Worked example A. Peak demand 50 L/s FAD for a 30-second burst, P_max 800 kPa abs (700 kPa gauge), P_min 700 kPa abs (600 kPa gauge):

V = (50 x 30 x 101.3) / (800 − 700) = 151,950 / 100 = 1,519.5 L.

Worked example B. Peak demand 12 L/s FAD for a 30-second burst, same pressures:

V = (12 x 30 x 101.3) / (800 − 700) = 36,468 / 100 = 365 L.

A 365 L receiver suits this profile, NOT 3,205 L. The 10x error common in older sizing tools comes from incorrect application of the pressure-ratio term, treating it as a multiplier rather than as the denominator of an absolute-pressure differential.

The formula assumes isothermal expansion (slow burst, full thermal exchange with tank walls, typical for bursts of 5 seconds or longer). For adiabatic fast bursts under 1-2 seconds, increase receiver volume by approximately 30% to allow for thermal-state recovery between bursts.

Aerial view of industrial facility with compressor room for compressed air system energy audit

Power basis: shaft kW versus total electrical input kW

Don’t audit shaft kW as if it were the site electricity bill. Compressor manufacturer datasheets typically quote shaft power, the kW input to the airend rotor. To convert to total electrical input, divide shaft kW by motor efficiency (typically 0.92-0.95 for IE3 or IE4 motors above 7.5 kW) and divide again by drive efficiency (0.97-0.98 for VSDs, 1.00 for direct-drive star-delta).

A 75 kW shaft compressor draws 80-86 kW total electrical input under typical conditions:

Premium IE4 motor plus direct drive: 75 / 0.94 / 1.00 = 79.8 kW
Modern IE3 plus VSD: 75 / 0.93 / 0.98 = 82.3 kW
Older motor plus older VSD: 75 / 0.92 / 0.97 = 84.0 kW
High-end conservative: approximately 86 kW

Audits MUST use total electrical input kW for cost calculations. Using shaft kW understates true energy spend by 8-15%. Every kW figure in an audit report should declare which basis it uses. “75 kW (shaft)” and “82 kW (total electrical)” are not interchangeable, and the recommendations register changes materially when the basis is corrected.

Specific power benchmarks

If you don’t measure specific power, you don’t know whether the compressor is making air or just making heat. Specific power, kW per L/s FAD or kW per 100 cfm, is the most diagnostic single metric in a compressed-air energy audit (per US DOE, Compressed Air Systems tip sheets). Industry-typical 2025 benchmarks at full load:

Modern VSD rotary screw: approximately 18 kW per 100 cfm (6.4 kW per m³/min FAD; 0.38 kW per L/s FAD).
Older fixed-speed at part load: 25-34 kW per 100 cfm (9-12 kW per m³/min FAD; 0.55-0.71 kW per L/s FAD).
Centrifugal at design point: approximately 16 kW per 100 cfm (5.65 kW per m³/min FAD; 0.34 kW per L/s FAD).
Small reciprocating: 20-23 kW per 100 cfm (7-8 kW per m³/min FAD; 0.42-0.48 kW per L/s FAD).

A site running 9 kW per m³/min where 6.5 is achievable is consuming roughly 38 per cent more energy than the benchmark at the compressor, before considering distribution losses. The first-pass audit calculation, measured kWh divided by measured FAD output, compared against the appropriate benchmark above, gives an immediate gap-to-best-practice estimate. Pin that number to the marginal tariff and you have the headline AUD savings figure for the recommendations register.

Need an Energy Audit for Your Compressed Air System?

Tell us your compressor make and kW, annual operating hours, current pressure setpoint, and what’s prompting the audit (energy bill, reliability concern, capital review). We review every enquiry and connect you with an Australian compressed-air auditor whose calibration and ISO 11011 methodology match your operation. Independent matching. Direct email acknowledgement within one business day; supplier match or status update within five business days.

Describe Your Application

Audit methodology under ISO 11011:2013

An audit without logged data is a sales visit with a clipboard. So the ISO 11011:2013 framework matters because it structures compressed-air assessments around evidence, not memory (per ISO, ISO 11011:2013 catalogue abstract). Data to collect over a representative cycle (1-2 weeks single-shift, 2-3 weeks multi-shift):

15-minute logged compressor electrical input in kW
Header pressure logged at 1-minute intervals
Total flow at compressor discharge (preferred) or estimated from compressor hours and nameplate FAD
Leak survey via ultrasonic detection during a planned non-production window. Use the leak cost calculator to convert orifice size and pressure into the annual AUD figure for the recommendations register
End-use audit identifying inappropriate uses (open blowing, abandoned drops, oversized regulators)

Output deliverables that justify the audit fee:

Baseline spend: annual kWh and AUD at the actual marginal tariff.
Opportunity register: itemised by leak repair, pressure reduction, sequencing optimisation, end-use elimination, drying technology change.
Per-opportunity economics: payback in months and 5-year NPV, with the data file behind each number disclosed.

What to ask of an audit provider

A manufacturer’s “free” audit isn’t free if it steers the answer before the data is logged. Independent provider versus manufacturer audit: a manufacturer’s audit optimises toward that manufacturer’s equipment recommendations. An independent audit optimises toward lowest total-cost outcome regardless of brand (per CAGI, Working with compressed air buyer guidance).

Questions that distinguish the two:

What flow-measurement instrumentation will be used and what is its current calibration certificate?
What sample-rate logger, and for how many days?
Does the provider have any commercial relationship with the equipment they will recommend?
Will the audit report disclose calculation assumptions and source data files?
Is the audit conducted under ISO 11011:2013 or equivalent?

The answers reveal whether the audit is independent or sales-led. CAS connects facilities with independent audit providers who satisfy the questions above.

Sourcing an independent compressed-air audit

What CAS does. We match Australian operators (manufacturing plants, mining sites, food and beverage facilities, automotive workshops) to independent compressed-air auditors with calibrated flow instrumentation, ISO 11011:2013 methodology, and no commercial tie to a single OEM brand. The match is tuned to your facility scale, your tariff, your operating shift pattern, and the specific evidence your finance team needs to sign off the resulting capital recommendations.

What to send us. Facility type (manufacturing, mining, food, automotive, etc.), installed compressor make and rated kW, annual operating hours, current pressure setpoint, the postcode, and a one-line description of what’s prompting the audit (energy bill increase, reliability concern, capital review, sustainability reporting). We’ll acknowledge inside one business day. Auditor shortlist matched to your category within five business days.

Frequently Asked Questions

How big a receiver does my compressed air system actually need?

Size receivers from short-burst peak demand using V = (Q_peak x t_burst x P_atm) / (P_max − P_min), with Q in L/s FAD, t in seconds, P in absolute kPa. A 12 L/s FAD burst for 30 seconds with 100 kPa swing (700-800 kPa abs) needs 365 litres, not the 3,000-plus litres the wrong formula returns. The most common mistake is treating the pressure ratio as a multiplier instead of the absolute-pressure denominator. For very fast bursts under 1-2 seconds, add about 30 percent for thermal recovery.

Why does the audit need shaft kW and total electrical input kW separately?

Because they aren’t the same number. Manufacturer datasheets typically quote shaft kW at the airend. The site electricity meter sees total electrical input, which is higher by motor and drive losses. Divide shaft kW by motor efficiency (0.92-0.95 for IE3 or IE4 above 7.5 kW) and again by drive efficiency (0.97-0.98 for VSDs, 1.00 for direct-drive). A 75 kW shaft compressor draws 80-86 kW from the meter. Auditing against shaft kW understates energy spend by 8-15 percent and leaves money on the table at the recommendations stage.

What specific power should my compressor be hitting?

Specific power is kW per 100 cfm (or kW per m³/min FAD). 2025 benchmarks at full load: modern oil-injected rotary screw with VSD about 18 kW per 100 cfm (6.4 kW per m³/min FAD; 0.38 kW per L/s FAD); centrifugal at design point about 16 kW per 100 cfm (5.65 kW per m³/min FAD; 0.34 kW per L/s FAD); older fixed-speed rotary screw at part load 25-34 kW per 100 cfm (9-12 kW per m³/min FAD); small reciprocating 20-23 kW per 100 cfm (7-8 kW per m³/min FAD). If your measured kWh divided by measured FAD lands above the achievable benchmark for your machine class, you are running roughly 30 to 40 per cent above the achievable benchmark at the compressor before distribution losses are even counted.

What does an ISO 11011:2013 compliant audit actually involve?

Logged data over a representative cycle: 15-minute interval compressor electrical input in kW, header pressure at 1-minute intervals, total flow at the compressor discharge (or estimated from compressor hours and nameplate FAD), an ultrasonic leak survey during a planned non-production window, and an end-use audit identifying inappropriate uses (open blowing, abandoned drops, oversized regulators). Single-shift sites need 1-2 weeks of data; multi-shift sites need 2-3 weeks. The deliverable is a baseline kWh and AUD spend at your actual marginal tariff plus an itemised opportunity register with per-opportunity payback in months and 5-year NPV.

Should I use the equipment manufacturer or an independent auditor?

A manufacturer audit optimises toward that manufacturer’s equipment recommendations. An independent audit optimises toward lowest total-cost outcome regardless of brand. Test the distinction with these questions: what flow-measurement instrumentation will be used and what is its calibration certificate; what sample-rate logger and for how many days; does the provider have any commercial relationship with the equipment they will recommend; will the audit report disclose calculation assumptions and source data files; is the audit conducted under ISO 11011:2013 or equivalent? If the answers waver, the audit is sales-led, not independent.

Get Matched with an Energy Audit Specialist

Describe your compressed air system and the savings figure your finance team needs proved. We review every enquiry, confirm the scope, and connect you with an independent Australian compressed-air auditor whose calibration certificates and ISO 11011 methodology match the brief.

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Compressed air audits by city

This national guide covers the audit methodology that applies anywhere in Australia. For the local funding and sourcing picture in a specific capital, including the state energy-incentive schemes that can offset the upgrades an audit finds, see the national overview: compressed air audit Australia, which covers the audit methodology under ISO 11011 plus the state-by-state funding landscape across NSW (Energy Savings Scheme), Victoria (Victorian Energy Upgrades), and the time-limited rebate rounds in Queensland, Western Australia, South Australia, Tasmania, ACT and NT.

Related Resources

Compressed Air for Mining: site-scale demand profiles, remote-operations specifics, and audit priorities at hard-rock and underground operations.
Air Compressor Sizing Guide: turning audit findings into a defensible right-sized replacement specification before going to market.
Heat Recovery ROI Calculator: quantify the fuel saving and payback period when an audit recommends a compressor heat-recovery retrofit.
Leak Cost Calculator: convert leak orifice size and pressure to annual AUD waste for the recommendations register.
Compressed Air Leak Detection: ultrasonic survey methodology, repair prioritisation, and ongoing leak-management programme design.

General information disclaimer. The information on this page is general in nature and provided for educational purposes only. It is not engineering, safety, or professional advice, and it does not account for the specifics of your site, equipment, or duty. Compressed air system design, pressure equipment selection, and regulatory compliance must be confirmed with a qualified engineer and the relevant work health and safety regulator before you act. Compressed Air Solutions is a publisher and referral service, not a licensed engineering practice, and accepts no liability for decisions made on the basis of this content. Verify all figures, standards references, and regulatory requirements against current primary sources.

Related: The Hidden Cost of Compressed Air Leaks in Australian Industry (2026) sizes the national cost of the leaks an energy audit uncovers.