Choosing an air compressor: air delivery, pressure and tank size

Intake or air delivery: which figure counts?

Makers give two figures in litres per minute. The intake is the amount of air the compressor draws in. The air delivery (also free air delivery or effective output) is the air that reaches the outlet at a given pressure. It is always well below the intake, which is why the intake is often printed large on the box.

Air tools have an air consumption in litres per minute that the maker states. Choose a compressor whose air delivery is above the consumption of the tool that needs the most air, with some margin. Otherwise the compressor keeps cutting in and the pressure drops while you work.

How much pressure do you need?

Workshop compressors usually reach a maximum pressure of 8 or 10 bar. Most air tools work at about 6 bar; you set the working pressure on the regulator with its gauge. Car tyres and balls need much less. What matters is that the compressor can hold your tool's working pressure.

Which tank size?

The tank stores compressed air. A large tank buffers more, so the motor starts less often, but it does not make more air. For short bursts, for example with an air nailer or stapler, a blow gun or a tyre inflator, a small tank is enough.

For tools that need air without a break, such as spray guns, air sanders or sandblasters, air delivery decides. A large tank then only helps at the start. With heavy compressors with a large tank, also check the wheels and weight if you want to move it around.

Oil-free or oil-lubricated?

An oil-free compressor needs no oil changes and is usually lighter. It suits DIY work with breaks. An oil-lubricated compressor needs care: you check the oil level and change the oil as the manual says. Makers often use it in workshop compressors for longer running times.

Some makers state the duty cycle in per cent: how long the motor may run within a period. For noise you find the sound power level in dB(A). Compressors sold as "silent" are quieter; always compare the stated dB(A) figure, though.

230 V, 400 V or cordless

Most compressors for home use run on a normal 230 V socket. Large workshop compressors often need a 400 V three-phase supply. Cordless compressors from the tool platforms are small and meant for tyres, balls and small jobs on the go; they use the batteries of your battery platform.

Quick coupling, hose and condensate

Quick couplings come in several systems that do not fit each other. Check that compressor, hose and tool use the same system, or plan for adapters.

Compressing air produces condensate in the tank. Drain it through the drain valve after work so the tank does not rust from the inside. For spraying, fit a water separator or filter between the compressor and the gun.

Comparing on ToolRango

Under compressors you find the models with the prices of every shop. Some compressors also come as a set with hose and accessories. Each version has its own EAN or part number, and ToolRango compares them separately, so you see what is in the box.