A pneumatic cylinder that pushes 100 pounds costs about $90. An electric actuator with the same force output costs $600 to $1,800 with its driver. On that comparison alone air wins every time, which is why most machine shops default to it and why a lot of machines get built with compressed air doing work it is bad at.

The comparison is wrong because it prices the cylinder and ignores the plant. Compressed air is the most expensive utility in a factory per unit of delivered work — a compressor converts roughly 10 to 15 percent of its electrical input into usable work at the tool. Once you account for the compressor, dryer, filtration, piping, and the leak rate every air system has, the picture shifts substantially.

What Air Actually Costs

A 25 hp rotary screw compressor delivering about 100 SCFM at 100 psi consumes roughly 20 kW loaded. At $0.11 per kWh across two shifts, that is on the order of $9,000 a year in electricity for one compressor, before maintenance and filter elements. Then there are leaks: a well-maintained system loses 10 to 20 percent of its output, a neglected one 30 percent or more.

The decision this drives is straightforward. If the plant already has an air system with spare capacity, the marginal cost of a few cylinders is small and pneumatics look excellent. If the machine requires a new compressor, dryer, and distribution run, you are adding $8,000 to $30,000 of infrastructure and an ongoing energy bill to save a few hundred dollars per axis. Electric wins that case decisively.

Precision and Control

Air is compressible, and that single fact defines the control boundary between the two technologies.

A standard pneumatic cylinder is a two-position device. It goes to one end or the other and stops because it hits metal, not because it was commanded to, so end repeatability is excellent — better than 0.05 mm. Mid-stroke positioning is where it falls apart: proportional pneumatic systems cost as much as a servo and still deliver 0.5 to 2 mm accuracy with poor behavior under changing load.

Electric actuators hold any commanded position with 0.01 to 0.1 mm repeatability, follow programmed velocity and acceleration profiles, and execute a controlled force limit through current control. They also report where they are, which is what makes a machine remotely diagnosable. The motor and feedback choices behind that are in choosing a motor for your product and how to choose a linear actuator.

Force control inverts the comparison. Pneumatics deliver a constant force set by regulator pressure and cylinder area, and they are compliant, so a clamp meeting an oversize part simply applies its force and stops. An electric actuator commanded to a position and blocked will fault or push until something breaks unless you implement torque limiting deliberately. For clamping and pressing against a variable stack, air is the better engineering answer.

Speed, Duty Cycle, and Heat

Pneumatics are fast. A small cylinder reaches 1 to 3 m/s easily, cycles several times per second, and does not care about duty cycle — 100 percent continuous cycling is normal, with heat leaving in the exhaust air. That is why high-rate packaging, sorting, and part-ejection machines are still overwhelmingly pneumatic.

Electric actuators run 0.2 to 1 m/s on a ball screw, with belt-driven units reaching 2 m/s at reduced force, and they have a thermal duty cycle: a motor held at stall generates heat with no motion to remove it. If your cycle is one motion every four seconds for sixteen hours a day, check the duty rating rather than the peak force. Cycle life is the reverse — pneumatic seals wear and get rebuilt, while a ball-screw axis is rated in tens of millions of cycles and usually outlasts the machine.

Noise, Cleanliness, and Environment

Exhausting cylinders produce 85 to 95 dBA at the machine, pushing an operator station into hearing-protection territory under OSHA 1910.95. Mufflers help by 10 to 15 dB and add backpressure. An electric axis runs at 55 to 70 dBA — not a small consideration for a machine near people all day. Air also carries what is in it: oil carryover and moisture end up wherever the exhaust points, which is why food, pharmaceutical, and cleanroom applications either specify oil-free compressors with dewpoint control or move to electric.

Pneumatics win two environments outright. In explosive atmospheres an air cylinder has no ignition source and no electrical classification burden. In wet, dusty, or high-vibration settings a sealed cylinder tolerates conditions that put an electric actuator's encoder and driver at risk unless the assembly is properly rated, a topic running through IP ratings and seal and gland design.

Maintenance and Who Fixes It

Pneumatic maintenance is frequent, cheap, and simple: drain the water traps, change filter elements, replace a $40 seal kit, swap a $70 solenoid valve. Any technician can do it with hand tools, and the failure modes are visible and audible. Electric maintenance is rare, expensive, and needs a different skill set — a ball screw runs for years between relubrications, but a failed driver is a $900 module plus a technician who understands parameter sets and homing procedures. For a machine going into a plant with maintenance staff but no automation staff, that difference is a real deployment risk and belongs in the commissioning plan described in industrial machine development.

How to Decide, Axis by Axis

The right answer for most machines is hybrid, chosen per motion rather than per machine.

  • Use pneumatic for two-position motion, clamping with a force target, high cycle rates, hazardous atmospheres, and any simple axis where the plant already has air.
  • Use electric for multi-position or profiled motion, anything needing position feedback or recipe changes between products, quiet environments, machines shipped to sites with no air, precise force-versus-position control, and axes where energy cost over a decade matters.
  • Watch the hidden constraint: a machine sold to many customers has to work in the worst customer's plant, and designing around available compressed air makes it dependent on a utility you do not control.

Costing the options honestly means building both bills of materials with the infrastructure line included, then comparing throughput and flexibility. That analysis belongs in the same conversation as deciding when automation pays at all.

Designing the Motion Architecture

Projects House designs machine motion axis by axis: force and cycle requirements, actuator selection with infrastructure cost included, controls architecture, and a maintenance story your customer's plant can support. Send your requirements through the contact form.