For electricity, gas, and water, there is an invoice at the plant. Not for compressed air. It is available at every wall, is used as a matter of course, and does not appear as a separate item in any cost center. In many operations, compressed air is therefore regarded as a practically free medium—and at the same time is monitored less rigorously than any other energy carrier.

In fact, compressed air is not a raw material but a converted operating resource. Electrical energy is transformed into pressure, and a large portion of the energy input leaves the compressor again as heat. Compressed air generation accounts for approximately 7% of industrial electricity consumption in Germany. For a well-utilized industrial compressor, energy costs constitute by far the larger portion of life cycle costs; figures of 65 to 85% are cited in the technical literature.

This article shows how to calculate compressed air cost per m³, which four variables determine it, and which three assessments a plant can perform using existing operating data.

Why Compressed Air Is Underestimated in Operations

Three factors converge. First, the meter is missing: The electricity consumption of the compressors is embedded in the plant’s total invoice and is rarely allocated to a line or process. Second, the purchase price is visible, but operation is not. The system is paid for once; the air, every day. Third, rising consumption is hardly noticeable as long as the network pressure remains stable: The compressor automatically compensates for additional losses as long as it has reserve capacity.

This shifts perception. A system that runs reliably is considered to be in order—even if it generates significantly more air than production actually requires.

What One Cubic Meter of Compressed Air Costs in Generation

The price per cubic meter is not listed in any table. It results from your own system. The key figure for the basic calculation is the compressed air energy index of generation: the electricity consumption of the compressed air generators including controls, frequency converters, fans, and other auxiliary units, divided by the compressed air volume generated in the same period. It is expressed in kWh/m³. The energy consumption of dryers and other active components of compressed air treatment is not included. It must be recorded separately, allocated to the generated compressed air volume, and additionally accounted for in the complete operating cost calculation. Pressure losses through dryers, filters, and piping must also be included in a complete system analysis.

For an operating pressure of 7 bar (g), a range of 0.10 to 0.12 kWh/m³ is considered a good to acceptable value. If the determined index is significantly higher, root cause analysis is worthwhile. The compressed air energy index of generation describes the generation system and indicates how much electricity the compressed air generators, including the mentioned auxiliary units, require per cubic meter generated.

The specific power requirement, by contrast, describes an individual machine and relates its total electrical power input to its delivery volume (FAD) as specified in the data sheet according to ISO 1217. Machines can only be reliably compared if delivery volume, operating pressure, and reference conditions match. The rated motor power in kW is unsuitable for both analyses.

Electricity costs of compressed air generation per m³ = compressed air energy index of generation (kWh/m³) × energy rate (€/kWh)

Additional electricity costs of treatment per m³ = energy consumption of treatment (kWh) ÷ generated compressed air volume (m³) × energy rate (€/kWh)

For the complete ongoing energy cost calculation, both values must be added. The following sample calculation shows only the first part, i.e., the electricity costs of compressed air generation.

Sample Calculation: Electricity Costs of Compressed Air Generation

Note: Sample calculation with disclosed assumptions. The values are not transferable to other systems and do not replace measurement.

• Delivery volume: 5 m³/min
• Operating hours: 4,000 h per year
• Compressed air energy index: 0.110 kWh/m³ (assumption, 7 bar)
• Energy rate: €0.22/kWh (assumption)

Annual volume: 5 m³/min × 60 × 4,000 h = 1,200,000 m³. Electricity consumption: 1,200,000 m³ × 0.110 kWh/m³ = 132,000 kWh. Electricity costs: 132,000 kWh × €0.22/kWh = €29,040. This corresponds to approximately 2.4 cents per cubic meter for compressed air generation, excluding the energy requirements of treatment.

Two variables determine the result: how much air is generated and how much energy each cubic meter costs. How to determine the actually required volume is shown in the guide to calculating compressed air demand.

Generation Costs Are Not the Complete Total Costs

The calculations above answer a clearly defined question: What does ongoing operation cost per cubic meter generated? They are thus an operating or energy cost calculation, not a complete analysis of total operating costs.

For a complete life cycle analysis, the following must also be included: purchase price of compressors and treatment equipment, installation, piping, electrical connection and, if applicable, foundation, maintenance, wear parts and spare parts, depreciation and financing, modifications due to demand changes, and residual or disposal value at the end of the service life. Only this sum yields the total costs. How the individual components are distributed over the service life is addressed in the article on the total costs of an industrial compressor.

The Cost Driver Model: Four Key Variables

In a simplified model, four key variables can be distinguished. The first two operate multiplicatively: Improving both by ten percent reduces the electricity costs of generation by approximately one-fifth.

1. Generated Volume. Every cubic meter that is not needed still costs. This includes leaks, continuous blowers, consumers that remain connected outside of shifts, and applications for which compressed air is not the appropriate medium.
2. Compressed Air Energy Index. It summarizes how much electricity generation requires per cubic meter. This is influenced by pressure setpoint, compression technology, control strategy, utilization, maintenance condition, and all pressure losses between compressor and point of use.
3. Energy Rate and Heat Recovery (HR). The price per kWh directly affects every cubic meter. The majority of electrical drive energy is converted into heat. Part of this heat can be utilized via heat recovery (HR). Where a suitable heat sink is available and heat generation and heat demand coincide temporally, HR reduces the plant’s total energy costs because it replaces heat that would otherwise be purchased.
4. Fixed Ancillary Costs. Maintenance, filter and oil changes, wear parts, dryer maintenance, and condensate treatment continue independently of the volume consumed.

The sequence is deliberate: Volume and compressed air energy index can usually be influenced more quickly and cost-effectively in existing systems than the energy rate or a new investment.

Where Costs Arise in Daily Operations

Leaks

Leaks are continuous consumers. They draw air at night, on weekends, and during breaks—precisely when no cubic meter generates benefit. As a guideline: In smaller networks, the leak share should not exceed approximately 5%; in larger industrial networks, around 10%; in very large networks, approximately 13 to 15%. Studies in industrial operations show, however, that the actually measured shares are frequently significantly higher.

Typical locations are quick couplings, hoses, fittings, service units, valves, and cylinder seals. The compressed air station itself is also a candidate, for example via stuck condensate drains or defective relief valves. It is important to separate two questions: The mathematically derived leak share indicates how much is lost. Where the leaks are located is only revealed by detection, typically using ultrasound during operation.

Pressure Setpoint and Pressure Losses

The required pressure level begins at the consumer, not at the compressor. The pressure setpoint of the station results from the process pressure at the most sensitive consumer, the permissible tolerance, the pressure losses across treatment and network, and a justified safety margin. Each bar of higher compression increases energy requirements by approximately 6 to 10%; the exact value depends on the system, control, and load profile. Which pressure level suits which network is addressed in the article on the correct operating pressure.

As a guideline, the pressure drop from the compressed air receiver to the consumer should not exceed one bar, with the predominant portion typically occurring in connection accessories—in hoses, couplings, filters, and service units—and only a small portion in the pipe network. The most common mistake is pressure increase as a quick remedy. Before the pressure setpoint rises, contaminated filters, dryer condition, couplings, hose cross-sections, pipe network routing, load peaks, and individual critical consumers should be examined.

No-Load Operation and Load Cycling

A compressor with load/no-load control consumes energy even when it is not delivering air. The power requirement during no-load operation is typically 20 to 30% of loaded operation. Short load cycles, an undersized compressed air receiver, or multiple machines without master control extend these unproductive phases. Variable speed control adapts delivery volume to demand and reduces no-load operation and switching cycles. Whether it pays off is determined by the measured load profile, not the brochure: Variable speed machines operate most economically in a medium utilization range. At full load, the losses of the frequency converter are added. Only with permanent magnet synchronous motors can the higher motor efficiency partially offset these converter losses. This does not apply to variable speed compressors with asynchronous motors.

Compression technology also contributes to this driver. In the STRONG 2S series, two-stage compression with intercooling reduces energy requirements; according to the catalog, over 10% energy can be saved compared to single-stage compression. Why two machines with the same rated motor power deliver different amounts of air per kilowatt-hour is explained in the article on the two-stage screw compressor.

Treatment and Condensate

Dryers, filters, and condensate technology cost twice: through their own energy consumption and through the pressure drop that the station must compensate for. A rising filter differential pressure due to loaded elements drives the pressure setpoint upward; as a guideline, the pressure drop across a line filter should not exceed 0.1 bar. Adsorption dryers additionally require purge air, which the compressor must first generate. Which design is necessary when is clarified in the comparison refrigerated dryer and adsorption dryer.

A frequently overlooked item is condensate drains. A defective or permanently open drain continuously loses compressed air; unfavorably set timer-controlled drains release more air than necessary with each cycle. How the chain of separator, dryer, filter stages, and condensate technology interacts is described in the guide to compressed air treatment. The basic principle: Higher air quality than the process requires increases investment and operating costs without benefit.

The First Three Assessments for Your Plant

The following assessments work with existing operating data. They provide an initial classification and indicate whether reliable measurement is necessary. They do not replace reliable measurement.

1. Evaluate Load and No-Load Hours. Read the operating hour and load hour counters. The difference yields the no-load hours. If the no-load share is below approximately 10% of total operating hours, this is unremarkable; above that, examination of run-on time, receiver size, machine sizes, and master control is worthwhile. Record the counter readings monthly going forward—an unexplained increase is often the first indication of a new problem.
2. Check Consumption During Production Standstill—Under Appropriate Conditions. If a compressor regularly loads during production standstill, it is working against leaks and continuous blowers. The leak share can be roughly estimated from the ratio of load time to total time during standstill.

This estimate is only meaningful under certain conditions. It assumes that production is actually stopped and known continuous consumers are calculated out beforehand. It works with machines that count load and no-load times separately; with variable speed compressors, no air volume can be derived from the runtime ratio because delivery volume varies with speed. The underlying delivery volume comes from manufacturer specifications and may deviate due to wear or compressor-internal leaks, which is why good maintenance condition is a prerequisite. In operations with continuous production, the method is not applicable; here, measurement-based alternatives are required. And where compressed air supplies safety-relevant functions, the supply must not be interrupted for the assessment.

• Compare Pressure Setpoint Against Actual Demand. Determine the required pressure at the most sensitive consumer and compare it with the pressure setpoint at the station. The difference is your allowance for pressure losses and safety. Read the differential pressure indicators on upstream and downstream filters and check the condensate drains for continuously blowing or excessively long-opening valves.

If these assessments reveal anomalies, the next step is worthwhile. For precise quantification of delivery volume, base load, peak load, and no-load share, measured values over a representative operating week under real operating utilization are required; a compressed air audit provides this data basis.

Common Errors in Cost Analysis

• Comparing compressors solely by rated motor power in kW instead of by specific power requirement relative to delivery volume.
• Comparing delivery volumes without common reference conditions.
• Increasing the pressure setpoint before the cause of the pressure drop is localized.
• Determining the leak share once and then not tracking it further.
• Excluding treatment, condensate technology, and piping from the cost calculation.
• Adopting a flat cent value per cubic meter instead of calculating with your own operating data.

Frequently Asked Questions

Why Is Compressed Air More Expensive Than the Electricity That Generates It?

Because during compression, the predominant portion of electrical energy is released as heat, and only a fraction arrives as usable compressed air at the tool. Added to this are losses in the network, in treatment, and through leaks. Comparing the energy requirements of a compressed air-powered application with a suitable direct electric drive for the same task, the compressed air solution is typically significantly more energy-intensive. How large the difference is, however, depends heavily on the application, pressure level, efficiency, and load profile.

For Which Applications Is Compressed Air Not Worthwhile?

Wherever a simpler form of energy accomplishes the same task. For blow-off, an industrial vacuum is usually the better choice; for cooling and conveying, a blower or conveyor belt; for drives, an electric motor; and for linear motion, possibly a linear actuator or hydraulics. Where compressed air remains the technically correct choice, optimized nozzles and demand-based control noticeably reduce consumption.

How Strongly Does Intake Temperature Affect Costs?

Warm intake air has lower density, so the compressor must draw in a larger volume for the same air mass. If intake temperature rises from 20°C to 35°C, specific power requirement increases by approximately 5%. Supply air, exhaust air, and heat dissipation therefore belong in the cost analysis; the compressor room planning directly affects the price per cubic meter.

How Does Treatment Factor Into the Equation?

Compressed air treatment includes not only the dryer but also line filters and compressed air receivers. In a complete system analysis, piping and its installation method are additionally included. The energy and cost share of drying depends heavily on the drying method, the required pressure dew point, utilization, pressure drop, and control. Adsorption dryers can require significantly more energy than refrigerated dryers due to desiccant regeneration and purge air requirements. They are therefore only sensible where the process actually requires a negative pressure dew point. The difference arises primarily from desiccant regeneration and purge air requirements. An adsorption dryer is therefore only sensible where the process actually requires a negative pressure dew point.

Is Heat Recovery Worthwhile for Cost Calculation?

Mathematically almost always; practically only under conditions. The majority of electrical drive energy is converted into heat, and part of this heat can in principle be utilized. Decisive factors are the temperature level, a heat sink nearby, temporal overlap of heat generation and heat demand, and a sufficient number of full-load hours—no-load hours deliver little heat. The STRONG 2S series is optionally available with an integrated heat exchanger that makes compression heat usable as hot water.

Evaluate Compressed Air Costs Using Your Own Operating Data

A reliable cost analysis begins with your operating data. Helpful information includes the number and delivery volume of compressors, control strategy and year of manufacture, the set pressure setpoint and the pressure actually required at the point of use, operating and load hours, shift model, the energy rate per kWh, the existing treatment equipment, and known problems with pressure drop, leaks, or condensate.

On this basis, SCC air compressors provides a technical assessment of the situation and identifies the most effective drivers in your network. The scope of services includes inspection of the system for faults and leaks, analysis of compressed air demand with data logger, and simulation of compressor settings; from this, economic feasibility and savings calculations for your specific system are developed. An overview of suitable series is provided in the product overview. Describe your situation via the technical consulting of SCC—the more precisely operating data are available, the more concrete the assessment.