What Size Air Compressor Do I Need?
Choosing the correct size air compressor is important for ensuring your business has a reliable supply of compressed air without paying for more capacity than you actually need.
An undersized compressor may struggle to maintain pressure and run continuously, while an oversized compressor can increase purchase and energy costs unnecessarily.
So, how do you work out what size compressor you need?
1. Work Out Your Air Demand
The first step is to calculate how much compressed air your equipment requires.
Check the manufacturer’s specifications for each pneumatic tool or machine. Air consumption is usually given in CFM (cubic feet per minute) or m³/min.
Make a list of all the equipment that could be operating at the same time and calculate the total air requirement.
For example, if three machines each require 10 CFM and could operate simultaneously:
10 + 10 + 10 = 30 CFM
You would need a compressor capable of delivering at least 30 CFM, with an appropriate allowance for additional demand and future expansion.
2. Check the Required Pressure
Air flow isn’t the only consideration. You also need to know the pressure required by your equipment, which is normally measured in bar.
Many industrial pneumatic systems operate around 7–10 bar, but requirements vary depending on the application.
When selecting a compressor, make sure it can provide the required airflow at the pressure you need.
Remember that pressure can also be lost through pipework, filters, dryers and other components within the system.
3. Look at FAD, Not Just Motor Size
One of the most important figures to look at when comparing compressors is Free Air Delivery (FAD).
FAD tells you how much usable compressed air the compressor can actually deliver at a specified pressure.
Two compressors with the same motor size can have different air outputs, so simply choosing a compressor based on its kW rating isn’t enough.
Always compare the compressor’s FAD at your required operating pressure.
4. Consider How Often You’ll Use the Compressor
Your duty cycle is another important factor.
If you only need compressed air occasionally for tools or maintenance, a piston compressor may be suitable.
If compressed air is required throughout the working day for manufacturing, automation or production equipment, a screw compressor may be more appropriate.
For businesses with changing air demand, a variable speed compressor can also help match output to actual usage and improve energy efficiency.
5. Don’t Automatically Choose the Biggest Compressor
It can be tempting to buy the largest compressor you can afford, but bigger isn’t always better.
An oversized compressor may cost more to purchase and can consume more energy than necessary.
Instead, the compressor should be correctly matched to your actual air requirements, operating pressure and expected future demand.
If you’re planning to add machinery or expand production, however, it’s worth allowing for reasonable future growth.
6. Consider Peak Air Demand
Your average air consumption isn’t necessarily the same as your maximum requirement.
Some equipment may only use large amounts of air for short periods. If several machines start or operate at the same time, this can create a temporary increase in demand.
An appropriately sized air receiver can provide a stored supply of compressed air to help deal with short-term peaks and stabilise system pressure.
7. Check Your Existing System for Leaks
If you’re considering buying a larger compressor because your existing system isn’t maintaining pressure, check for compressed air leaks first.
Leaks in hoses, fittings, valves and pipework can waste significant amounts of compressed air and make an otherwise suitable compressor appear too small.
Repairing leaks can improve system performance and reduce energy consumption without necessarily requiring a larger compressor.
Example Compressor Sizes
As a general guide, compressor requirements might look something like this:
| Application | Typical Requirement |
|---|---|
| Small workshop | Compact piston compressor |
| Garage or maintenance work | Piston or small screw compressor |
| Several pneumatic tools | Larger piston or screw compressor |
| Engineering workshop | Screw compressor |
| Manufacturing or production | Industrial screw compressor |
| High or fluctuating demand | Variable speed or multiple compressors |
These are only general guidelines. The correct compressor size should always be determined from the actual airflow and pressure requirements of your equipment.
What Size Compressor Do I Need?
To choose the right compressor, you need to establish:
Total air demand + required pressure + duty cycle + peak demand + future requirements
Once these have been established, you can select a compressor with the appropriate FAD, pressure rating and motor size.
Need Help Choosing the Right Compressor?
Air System Controls supplies a wide range of piston and screw compressors, including fixed-speed and variable-speed models, receiver-mounted compressors and systems incorporating refrigerated dryers.
If you’re unsure what size compressor you need, our team can help assess your requirements and recommend a suitable solution for your application.
Contact Air System Controls to discuss your compressed air requirements.