Guide · Compressed air energy
How much do compressed air leaks and idle running cost a Malaysian factory?
In short
Two quiet losses sit inside most compressed air bills. Leaks: a plant that has not been well maintained typically leaks about 20% of its compressor capacity, and sometimes 20 to 30%, while a plant with a proper leak programme can keep it under 10%. Idle running: a rotary screw compressor running unloaded still draws about 15 to 35% of its full-load power while making no useful air. Both figures come from the US Compressed Air Challenge fact sheets listed below. To put a ringgit figure on them, measure each compressor's kWh and multiply by the rate on your own electricity bill.
This guide is about the money that leaves through holes in the pipework and through compressors that run without producing air. If you want to know what to measure on a compressor and how to set up energy logging in the first place, read our company guide on how to monitor air compressor energy consumption. It also covers pressure set points, so we don't repeat that here.
Why are leaks and idle running so easy to miss?
The Compressed Air Challenge calls compressed air "probably the most expensive form of energy available in a plant". Yet most factories never see that cost on its own. The whole plant sits behind one electricity meter, so the compressors' share disappears into a single monthly bill.
Leaks are, in the words of Fact Sheet #7, "almost impossible to see", and their hiss is easily lost in production noise. Unloaded running is even harder to spot: the motor is turning and the compressor sounds busy, but it is not delivering air. Neither loss shows up unless somebody measures each compressor separately.
How much air does a typical factory lose to leaks?
According to Compressed Air Challenge Fact Sheet #7, leaks can waste 20 to 30% of a compressor's output. A typical plant that has not been well maintained will likely leak about 20% of its total production capacity. A proactive leak detection and repair programme can bring that below 10%.
The energy is only part of the cost. The same fact sheet notes that leaks:
- drop system pressure, so air tools work less efficiently and production can suffer;
- force compressors to cycle more often, which shortens the life of almost all system equipment, including the compressor itself;
- add running time, which brings extra maintenance and more unscheduled downtime;
- can lead a plant to buy compressor capacity it does not need.
The most common leak points are couplings, hoses, tubes and fittings; pressure regulators; open condensate traps and shut-off valves; and pipe joints, disconnects and thread sealants.
What does a single leak cost per year?
Fact Sheet #7 prices three leak sizes at a fixed US electricity rate. We have converted those costs back into kWh so you can apply your own tariff.
| Leak hole diameter | Cost per year in the fact sheet | Energy per year (our estimate) |
|---|---|---|
| 1/16 inch (about 1.6 mm) | US$523 | about 10,500 kWh |
| 1/8 inch (about 3.2 mm) | US$2,095 | about 41,900 kWh |
| 1/4 inch (about 6.4 mm) | US$8,382 | about 167,600 kWh |
The fact sheet's costs assume an electricity rate of US$0.05 per kWh, constant operation and an efficient compressor. The kWh column is our estimate: the fact sheet's cost divided by US$0.05. If your air system is only pressurised for part of the year, scale it down by that share of hours (also an estimate). Multiply the result by your own rate per kWh to get a ringgit figure.
The point of the table is the shape, not the exact number: doubling the hole size roughly quadruples the cost. A handful of small leaks across a plant can add up to more than one large one.
How much power does a compressor use when it is running but not making air?
Many screw compressors use load/unload control. Compressed Air Challenge Fact Sheet #6 explains that the motor runs continuously and the compressor unloads when discharge pressure is high enough. In most cases an unloaded rotary screw compressor consumes 15 to 35% of its full-load power while delivering no useful work.
Illustrative estimate, not measured data: a 75 kW screw compressor running unloaded would draw roughly 11 to 26 kW. If it spends 1,000 hours a year unloaded, during breaks, quiet night shifts or weekends with little demand, that is roughly 11,000 to 26,000 kWh a year spent making no air.
Leaks and idle running feed each other. When nothing in the plant is using air, leaks still drain the system, so the compressor keeps loading and unloading just to hold pressure.
How can you estimate the losses in your own plant?
- Measure each compressor's energy. Fact Sheet #9 gives a quick formula for a compressor at full load: motor horsepower × 0.746 (to convert to kW) ÷ motor efficiency × annual running hours × electricity cost per kWh. A per-compressor kWh meter replaces the estimate with real numbers.
- Run a leak test. Fact Sheet #7 describes a test for compressors with start/stop controls: with all air-using equipment switched off, time how long the compressor runs on load (T) and off load (t). Leakage (%) = (T × 100) ÷ (T + t). Above 10% means the system can likely be improved.
- Look at non-production hours. When production stops, compressor energy should fall close to zero. Whatever is left is leaks, unloaded running or compressors that nobody switched off.
- Convert to ringgit. Multiply the wasted kWh by the energy charge on your electricity bill. Tenaga Nasional Berhad publishes its commercial and industrial tariffs; use the rate for your own supply category.
What should you fix first?
- The biggest leaks. The fact sheet recommends an ultrasonic acoustic detector, which picks up the high-frequency hiss of a leak. Soapy water brushed onto suspect joints also works, but takes longer.
- Equipment that is no longer used. Isolate it from the air system with a valve, because idle branches leak too.
- Off-shift running. Check which compressors keep running, loaded or unloaded, when production has stopped.
- A regular leak programme. Fact Sheet #7 recommends leak tests every quarter. A schedule only works if someone owns it: Service Tracker can schedule and record those maintenance visits for each machine.
- Re-check the compressor controls after repairs. The fact sheet notes that the control system should be re-evaluated once leaks are fixed, to capture the full saving.
Where does AirFinity fit in?
AirFinity logs energy (kWh), discharge pressure, temperature and run state (load, unload, stopped) for each compressor every minute, and shows them on a web dashboard and mobile app with alerts. That makes both losses visible every day: unloaded hours appear on each compressor's chart, and energy used outside production hours stands out against the shift pattern. See the features and technical specifications, or AirFinity on the Avantix Innovation website.
In one Penang manufacturing plant, six compressors were connected in about two weeks. The client reported around 40% less unexpected downtime and 25% energy cost savings within three months. Results depend on each plant's equipment and how the data is acted on.
Frequently asked questions
What percentage of compressed air is typically lost to leaks?
According to Compressed Air Challenge Fact Sheet #7, a plant that has not been well maintained will likely have a leak rate of about 20% of its total compressed air production capacity, and poorly maintained systems can lose 20 to 30%. A well-maintained system should lose less than 10%.
Does an unloaded air compressor still use electricity?
Yes. Under load/unload control the motor keeps running while the compressor makes no air. Compressed Air Challenge Fact Sheet #6 says that in most cases an unloaded rotary screw compressor consumes 15 to 35% of its full-load power while delivering no useful work.
How often should a factory test for compressed air leaks?
Compressed Air Challenge Fact Sheet #7 recommends carrying out leak tests quarterly, as part of a regular leak detection and repair programme.
How do I turn leak and idle running losses into ringgit?
Work out the wasted energy in kWh first, then multiply it by the energy charge per kWh on your own electricity bill. Tariffs differ by supply category and change over time, so this guide does not use a fixed ringgit rate.
Sources
- Compressed Air Challenge, Fact Sheet #2: Inappropriate Uses of Compressed Air (PDF), from Improving Compressed Air System Performance: A Sourcebook for Industry.
- Compressed Air Challenge, Fact Sheet #6: Compressed Air System Controls (PDF).
- Compressed Air Challenge, Fact Sheet #7: Compressed Air System Leaks (PDF).
- Compressed Air Challenge, Fact Sheet #9: Compressed Air System Economics (PDF).
- Tenaga Nasional Berhad, Pricing and tariffs for commercial and industrial customers. No tariff figures are quoted in this guide.
- Avantix Innovation, compressor energy monitoring case study, Penang. Figures as reported by the client.