Workshop compressors: delivered air beats brochure specs

The intake rating is on the box — the compressor has to work with delivered air

Three air-volume terms circulate in this category, and makers blur them by design. The intake rating is the theoretical swept volume of the piston, measured at the inlet and still free of any loss. It is the largest of the three numbers, works well as an eye-catcher, and often moves straight into the model name — Schneider UNM 260 or Einhell TE-AC 270/50/10. What actually reaches the impact wrench or spray gun is the delivered air, also called effective air delivery or FAD. That figure alone decides whether an air tool can be run at all. Which is why it leads this overview.

The gap between the two is no rounding error. As a rule of thumb, 40 to 65 percent of the intake rating arrives at the outlet — DIY direct-drive units near the lower edge, compressed-air specialists like Schneider or Kaeser near the top. The Kaeser Premium 250/24 W, for one, holds 144 l/min of delivery out of 250 l/min of intake, just under 58 percent — a good figure for a piston compressor. On simple direct-drive units that share shrinks to a quarter or a third, as the next section shows on documented numbers. Compare only the name number and you compare brochures, not compressors.

When “effective air delivery” is measured at zero bar

The trap does not end there, because even a stated delivery figure is not automatically the honest one. Many numbers that go under the label “effective air delivery” are in fact measured near zero bar — while filling the empty tank, where the compressor barely works against pressure. The Güde Airpower 190/08/6 quotes 145 l/min, measured at 0 bar; the Güde 400/10/50 N its 303 l/min likewise at 0 bar; the Scheppach HC53dc its 272 l/min at 1 bar. Under working pressure, where the tool draws its air, far less remains.

How much less shows in the cleanest counter-example in the field: the Scheppach HC25Si Silent states its delivery honestly at full working pressure — 59 l/min at 8 bar, from 230 l/min of intake. That is 26 percent. Similar is the Einhell TC-AC 190/24/8, whose 55 l/min at 7 bar make up only a third of its 165 l/min intake. Such numbers look meagre but are the reliable ones. Where the reference pressure is known, it stands alongside in the overview; only that lets you place 145 l/min at 0 bar next to 59 l/min at 8 bar at all.

Five devices make it even harder for the buyer and state no delivery at all: Einhell TE-AC 240/24 Silent, Schneider CompactMaster CPM 210, Michelin MB24, the Implotex whisper compressor and the Stanley D200/10/24V stand only on their intake rating. Their delivery cell in the overview stays empty accordingly — the name number alone proves no working output, and we do not flatter it into one.

Oil-free or oil-lubricated: the second dividing line

After air volume, lubrication is the feature that most clearly splits the 21 machines into two camps. Nine run oil-free, twelve oil-lubricated — and that is not a matter of quality but of use.

Oil-free means: no oil change, less weight, indifference to tilt and cold. The price is usually more noise and a shorter life under sustained load. The oil-free camp runs from the 8.4-kg lightweight Metabo Basic 160-6 W OF through the Silent machines Implotex (60 dB) and Scheppach HC25Si (60 dB) to the loud Stanley D200 at 97 dB. For occasional use, indoor work or dental technology, oil-free is the obvious pick.

Oil-lubricated means: quieter running, more continuous output, longer life — bought with regular oil changes and the rule not to tilt the unit far. Here sit the workhorses: Aerotec 220-24, Schneider UNM 260-10-50 W, Prebena VIGON 240, the twin-cylinder Güde 400/10/50 N and the Kaeser Premium. Anyone who needs air regularly and for longer stretches is better served in the oil-lubricated camp. In the overview the lubrication type has its own column, so the two camps separate cleanly.

Watts and horsepower say something about the socket, not the air

A common misreading concerns motor power. The watt or hp figure almost always describes the power draw from the socket, not the compressed-air output. “2 hp” equals about 1,500 W of input — a number that looks good but reveals nothing about how much air reaches the tool. In this field the input draw runs from 900 W on the small Metabo Basic 160-6 to 2,200 W on the Güde 400, Metabo Mega and Scheppach HC53dc.

More important than the raw wattage is the duty cycle. Many cheaper machines are built for intermittent use, not for hours of continuous running; a motor with a high rated draw that has to shut off after a few minutes helps little at the impact wrench. Motor power is therefore marked here as an input figure and grounds no ranking. One special case at the top end: the Metabo Mega 350-150 D pulls its 2,200 W as 400 V three-phase — it will not run off a normal domestic socket, which is worth settling before purchase.

Tank, pressure and weight: what the big tank does and what it does not

Operating pressure barely distinguishes the field: every machine works between 8 and 10 bar, enough for the usual air tools, which mostly run at 6.3 bar. Tank volume, by contrast, is spread wide — from 6 litres (Güde Airpower, Metabo Basic 160-6) through the bulk at 24 and 50 litres to 150 litres on the Metabo Mega. A large tank buffers demand peaks and lets the motor start less often, but it creates no extra air. Marketing likes to sell the tank as “power”; in fact tank capacity and delivered air are two separate quantities.

On weight the field parts by build: the portable 6- to 24-litre units weigh between 8.4 kg (Metabo Basic 160-6) and around 25 kg, the 50-litre class sits at a good 30 to 37 kg, and the stationary Metabo Mega with its 150-litre tank puts 85 kg on its wheels. Anyone who carries or stows the compressor often should factor that in; anyone who sets it up fixed in the workshop gains tank reserve and continuous running with the heavy machine.

Four camps in the field — from the DIY unit to the Kaeser

Before the number-crunching, the 21 compressors fall roughly into four groups.

DIY and home. Einhell (the German market leader, with the TC-AC, TE-AC and Silent lines), Güde, Scheppach, Stanley and Michelin cover the volume segment. Prices between about 85 and 310 €, often oil-free or a simple direct drive, for occasional to moderate demand.

Compressed-air specialists and semi-pro. Aerotec, Schneider Druckluft (UniMaster oil-lubricated, CompactMaster oil-free), ABAC and Prebena come from the compressed-air trade. Cleaner data sheets, often oil-lubricated, built for regular use.

Premium and professional. The Kaeser Premium 250/24 W stands alone at the top at 1,448.27 € — no data error but positioning: German piston engineering with corrosion-free stainless valve reeds, a damped intake filter and 78 dB at 250 l/min intake. It costs roughly sixteen times the cheapest machine and returns continuous-running reserves that a DIY direct drive does not have.

The silent class. Built for indoor rooms, practices or residential areas: the Implotex whisper compressor and Scheppach HC25Si Silent at 60 dB each, plus the Einhell TE-AC 240/24 Silent at 70 dB. Here noise is the selling point, not the delivered volume.

How much compressor the tool demands

In the end it is not the compressor that decides but the tool meant to hang off it. A tyre inflator, a blow gun or an air nailer draw only short bursts of a few litres — any 24-litre machine in the field covers that, and the choice tilts toward price, noise and weight. The Güde Airpower 190/08/6 (from 85.50 €), the Prebena VIGON 240 (187.19 €) or the Aerotec 220-24 (201.21 €) meet this demand.

As soon as a tool runs continuously, the sum changes. An impact wrench at around 350 l/min or a spray gun at 150 to 300 l/min overruns the delivered air of most 24-litre machines within seconds. Then the path leads to the 50-litre class with high delivery — Metabo Mega 350-150 D (220 l/min, though three-phase), Güde 400/10/50 N and Scheppach HC53dc — whose top figures, as shown above, are measured at low pressure and lie lower in reality. For a single user with one air tool, such a machine is often oversized; it pays off only where work is regular and runs for longer stretches.

Seven documented prices: from 85 euros to nearly 1,500

Seven of the 21 machines carry a price we read directly at the named shop on the day of retrieval — from 85.50 € for the Güde Airpower 190/08/6 to 1,448.27 € for the Kaeser Premium 250/24 W. In between sit the Prebena VIGON 240 (187.19 €), the Güde 260/10/50 (195.00 €), the Aerotec 220-24 (201.21 €), the Güde 400/10/50 N (269.00 €) and the Scheppach HC53dc (309.00 €). The span shows how far the category reaches: from the 24-litre entry unit to the professional piston machine lies almost sixteenfold.

A compressor price shifts with promotions and supplier. The documented values hold for the given retailer and the day of retrieval; today’s figure shows on the purchase link at the offer itself.