What does a buyer check before specifying an air compressor?
They check free air delivery at the working pressure they actually need, the specific power the machine draws to produce it, and the air quality class after treatment. Electricity is most of the lifetime cost of a compressor, so specific power decides the purchase more often than the capital price.
A plant engineer is comparing two machines with similar prices and very different electricity bills.
Reviewed 4 August 2026
Scope and specifications
- Free air delivery at stated pressure
- Capacity claimed without its pressure is not comparable.
- Working and maximum pressure
- Determines suitability for the application.
- Specific power
- Energy per unit of air, which dominates lifetime cost.
- Compressor type
- Reciprocating, screw, scroll and centrifugal suit different duty cycles and pressures.
- Lubricated or oil-free
- A hard requirement in food, pharmaceutical and electronics work.
- Air quality class after treatment
- The specification the process actually needs.
- Noise level and cooling requirement
- Decide where the machine can be installed.
Documents buyers may need
| Document | What it proves | Where it belongs |
|---|---|---|
| Performance datasheetAsked at: shortlisting | Free air delivery, pressure, specific power and noise under a stated test standard | Publish it |
| Test certificate for the specific machineAsked at: acceptance | Measured performance for the unit shipped, not the model | Per shipment |
| Air quality class certificationAsked at: oil-free and regulated applications | Purity class achieved for oil, water and particulates | Publish it |
| Declaration of ConformityAsked at: before shipment to regulated markets | Conformity with pressure equipment and machinery requirements | Publish it |
| Energy cost comparison basisAsked at: capital case | How lifetime running cost is calculated and on what assumptions | Publish it |
| Service schedule and parts listAsked at: total cost evaluation | What is serviced, how often and at what cost | Publish it |
| Warranty and service coverageAsked at: purchase decision | Period, exclusions and engineer coverage | Publish it |
Details for a useful enquiry
- Air demand and working pressure
- The basis of every selection.
- Duty cycle and shift pattern
- Determines the machine type and size.
- Air quality requirement
- Decides treatment and whether oil-free is needed.
- Existing installation
- What is being replaced and why.
- Site constraints
- Space, ventilation, noise limits and power supply.
- Electricity tariff
- Lets you make the lifetime cost case honestly.
Questions suppliers ask
Should we publish an energy cost comparison?
Yes, with the assumptions shown: hours of operation, electricity price, pressure and load profile. Buyers know energy dominates the cost of compressed air and are looking for someone to lay it out honestly. A comparison with its assumptions visible is persuasive; one without them is dismissed.
How should air quality classes be presented?
By naming the class for oil, water and particulates for each machine and treatment combination. Food, pharmaceutical and electronics buyers specify to a class, and a supplier who writes "clean, dry air" instead cannot be specified into those plants.
What matters most in a replacement purchase?
Why the last machine disappointed. Usually it is energy cost, unplanned downtime or air quality problems. Structuring your pages around those three failures, with real figures, reaches a buyer at the moment they are actually deciding.
Check which documents and standards your buyer needs; requirements vary by market, customer and contract.
Plact Research. Plact's editorial desk for buyer-evidence research. Industry standards, documents and buyer questions are researched and drafted with Plact's AI tools, then reviewed by Praveen Kavuri before publication. Every claim cites the standard, regulation or public source it rests on.
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