How to choose a cold-water pressure washer: bar, litres, motor

A cold-water pressure washer is chosen on three numbers: pressure in bar, flow in litres per hour and the power supply. Pressure and flow vary a lot from model to model: among the machines mentioned in this guide they range from the 5 bar of the Kärcher OC 3 portable cleaners to the 230 bar of the most powerful Annovi Reverberi models. To wash cars, tools and light surfaces, medium-pressure single-phase machines are enough; for building sites, workshops and heavy vehicles it is better to go up, with a more powerful and often three-phase motor. For small jobs away from the mains there are also battery models. Below you will find how to read the numbers on a data sheet, what changes between a portable machine and a trolley-mounted one, and what to ask before ordering.

The types

• Single-phase 230 V pressure washers. The Annovi Reverberi ranges carry a number in the name. The 6 Series 614 is portable and weighs 18.4 kg; the 614K has the same pump and the same performance (160 bar, 510 l/h, 2.9 kW), but it sits on a two-wheel trolley, has a 10 m hose instead of 8 m and weighs 24.6 kg. The 5 Series 589 is also trolley-mounted, with a hose reel: 170 bar, 500 l/h and 2.5 kW. In the 10 Series, the 1003 XE is single-phase at 230 V, with 150 bar and 630 l/h.
• Three-phase 400 V pressure washers. They are for intensive use and higher power. The Annovi Reverberi 11 Series 1120 is three-phase at 400 V, with 230 bar, 1,260 l/h and 9.3 kW in operation. In the same 10 Series as the 1003 XE there is the 1007 XE, three-phase at 400 V, with 230 bar and 900 l/h: the same series does not mean the same voltage, so always check it on the data sheet.
• Battery pressure washers. They work without a cable or socket, for quick washes where there is no power. The Makita DHW080ZK uses two 18 V LXT batteries; the DeWalt DCMPW1000N-XJ power cleaner uses 54 V FLEXVOLT batteries.
• Portable cleaners. Small and light, often with their own tank. The Kärcher OC 3 units, for example, work at low pressure (5 bar), with a tank of 4 to 8 litres and up to 15 minutes of battery: they are for bicycles, outdoor gear and small washes where there is no mains water.

How to choose according to the job

The features to look at

• Maximum pressure. It varies a lot from model to model: 5 bar for the Kärcher OC 3 cleaners, 24.8 bar for the battery mini, 80 bar for the Makita DHW080ZK, up to 230 bar for the Annovi Reverberi 1007 XE and 1120. High pressure removes caked-on dirt, but on delicate surfaces you work with wide nozzles or from a distance.
• Flow. It is measured in l/h or l/min. A high flow washes more surface in the same time and rinses better. It ranges from the 2 l/min (120 l/h) of the OC 3 cleaners and the 132 l/h of the battery mini up to the 1,260 l/h of the 1120 and the 1,300 l/h of the IPC PW-C50.
• Voltage and power. Mains machines are single-phase at 230 V or three-phase at 400 V; battery machines have a voltage that depends on the model. Among the Annovi Reverberi models mentioned, the catalogue gives 2.5 kW for the 589 and 9.3 kW in operation for the 1120: check the supply you have before choosing.
• Motor speed. Many professional data sheets state it. In the IPC sheets, for example, the 2-pole motor is given at 2,800 rpm and the 4-pole motor at 1,400 rpm; among the Annovi Reverberi models the 614 runs at 2,800 rpm, the 1003 XE and the 1120 at 1,450.
• Maximum inlet water temperature. It matters if you feed the machine with water that is already heated, and it varies from model to model: 40 °C for the Makita DHW080ZK, 50 °C for the 589 and the IPC PW-C50, 60 °C for the 614 and the 1120.
• Weight and size. Weight varies a lot: 2.2 to 2.3 kg for the Kärcher OC 3 cleaners without accessories, 18.4 kg for the portable 614, 24.6 kg for the trolley-mounted 614K, 110 kg for the 1120.

Bar, litres and kW: how to read the data sheet

Pressure and flow do not add up, they multiply. The hydraulic power of the jet, in kW, is pressure (bar) × flow (l/min) ÷ 600: it is a simple unit conversion. Calculation example: 150 bar with 600 l/h, that is 10 l/min, give 2.5 kW of hydraulic power. A real case: the 11 Series 1120 works at 200 bar with 1,260 l/h, that is 21 l/min, so it delivers 7 kW of hydraulic power, while the Annovi Reverberi catalogue states 9.3 kW in operation. The difference is the losses of motor and pump. This is why two machines with the same bar but different litres do not clean the same way.

Check the units: some data sheets give l/h, others l/min. To go from l/min to l/h, multiply by 60. Also check whether the value is maximum or working: for the 1120 the catalogue gives 230 bar maximum and 200 bar working.

On battery machines, voltage times capacity gives the nominal energy in Wh: an 18 V, 2.5 Ah battery makes 45 Wh, the battery of the mini (20 V, 2 Ah) 40 Wh. It is used to compare batteries with each other, not to predict how long the job will last: runtime depends on the machine and the pressure, and should be read on the data sheet or asked when ordering. Kärcher, for example, states up to 15 minutes for the OC 3 cleaners.

Whatever code the model has, pressure and flow are read on the data sheet, not in the name. The data sheets of the professional machines mentioned here state 50 Hz; some compact machines state 50-60 Hz, useful if they go abroad. The dedicated safety standard is EN 60335-2-79 (in Italy CEI EN 60335-2-79): it covers pressure washers without traction drive for household and commercial use, indoors and outdoors, with a rated pressure from 2.5 to 35 MPa, that is from 25 to 350 bar, and, within limits of capacity and pressure, steam cleaners.

What the data sheets say about some models

• IPC PW-C50. According to the IPC data sheet: pressure from 160 to 210 bar, flow from 1,000 to 1,300 l/h and absorbed power from 6.3 to 6.7 kW. The catalogue versions are three-phase at 400 V and 50 Hz, with 12 or 13 A of current, a 4-pole motor at 1,400 rpm, inlet water up to 50 °C and a weight of 68.2 or 70.1 kg. Ask which version you need and check the electrical panel before ordering.
• DeWalt DCMPW1000N-XJ. Power cleaner from the 54 V FLEXVOLT range, sold as a bare tool: DeWalt states that battery and charger are bought separately. It has a high and low speed selector and draws water from any fresh water source with the siphoning hose supplied. DeWalt mentions two nozzles, a foam cannon, the padded shoulder strap, an accessory bag and up to 60 minutes of runtime per charge with the DCB547 battery, measured with no load. Pressure depends on the setting: ask for it for the one you will use.
• Mini CPWLI20082. Battery of 20 V and 2 Ah, with 24.8 bar maximum pressure and 2.2 l/min flow, that is 132 l/h. It is a machine for touch-ups, not for washing a vehicle covered in mud.
• Kärcher OC 3 Plus. Low-pressure battery portable cleaner: Kärcher states 5 bar, flow up to 2 l/min, a 7 L tank, a 2.8 m hose, up to 15 minutes of runtime and 2.3 kg without accessories. In the OC 3 family the OC 3 (code 1.680-015.0) and the OC 3 + Bike (code 1.680-017.0) have a 4 L tank; the OC 3 Foldable has a foldable 8 L tank and a 1.8 m hose. At 5 bar it is not comparable with mains machines: it is for gentle washing on the go.

Before ordering, ask

• The required voltage (230 V, 400 V or battery) and the current draw, to compare with your installation.
• Pressure and flow together, with the unit (l/h or l/min) and whether they are maximum or working values.
• What is included: hose, lance, nozzles, gun and, for battery models, battery and charger.
• How the water is supplied: from the mains, with a suitable hose and fittings, or from a tank.
• The maximum inlet water temperature, if you use heated water.
• Where to get nozzles, seals and pump spare parts over time.

Common mistakes

• Choosing by bar alone. Flow counts too: at the same pressure, more litres mean faster work.
• Forgetting the electrical supply. A 400 V three-phase machine does not plug into a single-phase household socket: it needs a three-phase line.
• Using a compact machine every day. Compact machines are designed for short jobs: for continuous use you need a professional model.
• Running the pump dry. Always turn on the water and bleed the air from the gun before starting.
• Pointing the jet at people, animals, cables or tyres. The high-pressure jet can injure and cause damage: always keep it away.
• Leaving water in the machine in winter. Frost breaks the pump and hoses: drain it.

Frequently asked questions

How many bar are needed to wash a car?

Medium-pressure single-phase machines with a good flow are enough. For dried mud and site vehicles it is better to go up.

Single-phase or three-phase?

Single-phase runs at 230 V and suits medium use. Three-phase, at 400 V, is for more powerful machines and for working long hours every day, but it needs a suitable installation.

Does a battery pressure washer replace a mains one?

Not for heavy jobs. Battery models work at lower pressures: 80 bar maximum and 30 to 55 bar working for the Makita DHW080ZK, 24.8 bar for the battery mini, 5 bar for the Kärcher OC 3, against the 150-230 bar maximum of the mains Annovi Reverberi models mentioned here. They are fine for quick cleaning and where there is no power.

Can I use hot water in a cold-water machine?

Only within the maximum inlet temperature stated on the model's data sheet: for example 50 °C for the 589 and 60 °C for the 1120. To work with water heated by a burner you need a hot-water machine.

Can grease and oil be removed with a cold-water machine?

Yes with a good detergent, for light dirt. If the grease is abundant or dry, hot water works much better: talk to the technicians.

What do I do at the end of the job?

Switch off the machine and press the trigger to release the pressure, then disconnect water and lance. In winter drain the machine and protect it from frost.

You will find all the models in the cold-water pressure washers collection: to choose pressure and power supply, ask the AMES technicians for a quote or advice.