What does your cubic metre of compressed air cost?
Compressed air is free at the intake and expensive at the outlet. The formula fits on one line, and the figure that drives it, specific power, varies by about 20% between two screws of the same power. Here is how to calculate it for your installation.
The formula, and the only figure that drives it
The cost of a cubic metre of compressed air is calculated from the machine's specific power, that is, the kilowatts it absorbs to deliver one cubic metre per minute. Divide that specific power by sixty, and you get the kilowatt-hours consumed per cubic metre produced.
Then multiply by your price per kilowatt-hour, and you have the energy cost of the cubic metre. We do not give a kilowatt-hour price: yours depends on your contract, and an average figure would be of no use to you.
What remains is to add what the formula ignores: the cost of the machine over its life, maintenance and, above all, leaks in the network, which are paid for at the same rate as useful air while producing nothing.
| Energy per cubic metre | specific power (kW per 1 m³/min) ÷ 60 = kWh per m³ |
|---|---|
| Energy cost per m³ | kWh per m³ × your price per kWh |
| Annual energy cost | average absorbed power (kW) × running hours × price per kWh |
| What the formula leaves out | leaks, which consume without producing, and heat, which can be recovered |
The real specific power, family by family
This table is computed from the models in the CEZIUM catalogue, at their rated pressure. It shows what no sales brochure highlights: at equal power, a two-stage machine in the catalogue needs a median 20% less energy per cubic metre than a fixed-speed screw (16 to 32% depending on size), because it adds a permanent magnet motor and a drive to the second stage.
| Family | Models | kW/m³/min range | Median |
|---|---|---|---|
| Centrifugal turbo | 11 | 3.62 to 4.77 | 4.16 |
| Oil-free booster | 22 | 3.67 to 6.25 | 4.5 |
| Two-stage screw | 27 | 4.04 to 6.13 | 4.87 |
| Dual-motor rotary vane | 4 | 5.24 to 5.51 | 5.41 |
| VSD rotary vane | 7 | 5.24 to 5.95 | 5.45 |
| PM VSD rotary vane | 8 | 5.36 to 5.95 | 5.51 |
| Standard rotary vane | 11 | 5.24 to 6.11 | 5.56 |
| Super Silent rotary vane | 11 | 5.24 to 6.11 | 5.56 |
| Tank-mounted rotary vane | 4 | 5.4 to 6.11 | 5.75 |
| Onboard compressor | 4 | 5.4 to 7.55 | 5.86 |
| Oil-free water-injected screw | 36 | 5.46 to 7.1 | 5.9 |
| PM VSD screw | 33 | 5.31 to 7.33 | 5.98 |
| Fixed-speed screw | 32 | 5.31 to 7.33 | 5.98 |
| Oil-free dry screw | 20 | 5.43 to 6.62 | 6.1 |
| 3-in-1 integrated rotary vane | 5 | 5.64 to 6.52 | 6.35 |
| Oil-free rotary tooth | 14 | 6.11 to 6.52 | 6.38 |
| 4-in-1 integrated | 16 | 6.11 to 7.33 | 6.4 |
| Single-phase screw | 21 | 5.79 to 13.1 | 8.73 |
| Portable diesel | 46 | 6.65 to 12.26 | 9.17 |
| Oil-free scroll | 13 | 7.33 to 12.5 | 9.17 |
| 4-in-1 laser cutting | 22 | 8.22 to 14.01 | 11 |
| Stationary diesel | 7 | 10.17 to 15 | 12.08 |
| Oil-free piston 30 to 60 bar | 14 | 11 to 18.5 | 13.75 |
| High-pressure piston | 34 | 18.6 to 30 | 23.78 |
Calculated on the catalogue models at their rated pressure. Dryers, gas generators and low-pressure compressors are left out: comparing them here would read as an efficiency gain where there is only a lower pressure.
A two-stage compressor and a conventional fixed-speed compressor do not produce the same cubic metre at the same cost. On an installation that runs continuously, that gap weighs more than the purchase price of both machines.
The four levers, in the order they pay back
The order matters: the first two levers require no investment in machinery.
- Leaks: they consume twenty-four hours a day and produce nothing. A leak detection campaign is the first step, before any other decision.
- Operating pressure: every 0.1 bar reduction cuts consumption by about 0.6 to 0.7%. Many networks run higher than necessary to make up for pressure drops.
- Technology: two-stage on the base load, variable speed on fluctuating demand. The table above decides, not the installed power.
- Heat recovery: most of the absorbed energy leaves as heat, and a lubricated screw compressor gives it back through its oil circuit. It does not reduce the compressed air bill, it reduces the heating or hot water bill.
Why the purchase price misleads
Over the life of a compressed air installation, energy dominates the total cost by a wide margin: purchase and maintenance weigh far less than the cumulative electricity bill. A few points' difference in specific power therefore weighs far more, over time, than a difference in purchase price.
This is also what makes a comparison on installed power alone misleading. Two 75 kW machines can deliver different flows for the same consumption: the ratio between the two is what decides, and it is shown in the table above.
The questions we get asked
How many kilowatt-hours does it take to produce a cubic metre of compressed air?
What share of a compressor's cost goes on energy?
How can I reduce the cost of compressed air without changing the machine?
Recommended models for this topic
Selected by our technical team
Refine the calculation with your figures
Enter your power, your running hours and your kWh price. Annual saving, current bill and CO₂ avoided in 30 seconds.
Compressor heat recovery: up to 84% of the electricity can be reused
A screw compressor converts electricity into compressed air… and into heat. That heat accounts for 80 to 93% of the energy consumed, and 50 to 90% of that heat can be recovered to heat a building or a process. Method and calculation.
StandardHow to calculate and reduce pressure drop in a compressed air network
A 1 bar pressure drop costs around 7% in energy across the whole compressed air installation. Here is how to calculate it, measure it and reduce it: pipe diameter, network layout, filters, dryer, fittings.
GuideTwo-stage screw compressor: around 10% less energy than a standard screw
A two-stage screw compressor compresses air in two steps with intercooling in between, close to the theoretical isothermal cycle. Around 10% less energy than a standard screw at constant load; with a permanent magnet drive, on a variable load, the two gains combine.
Costs and energyPermanent magnet VSD: what the drive really saves
What a permanent magnet drive changes on a varying load: idle hours removed, and the annual gain to be worked out from your own load profile, across 6 typical power ratings.