Pressure Washer

Pressure washers use either gasoline or electric motors to power a pump that compresses water at a much higher pressure. Beyond these aspects, it’s important to understand the technical elements of each model to find a suitable washer for your cleaning needs.

Electric vs. Gas

There is no clear winner when it comes to gas vs. electric, as there are pros and cons for both.

Electric units are safe to use indoors because they don’t produce harmful fumes. Also, electric motors are usually quieter and require less maintenance than a gas engine. Finally, the user does not need to store or handle fuel for electric pressure washers, which can become an expense over time.

With a gas pressure washer, there are often a few different choices when selecting an engine. This allows for a variety of power levels to meet different needs. Also, gas engines don't require a power cord, allowing for more portability and freedom of movement.

Hot Water Vs. Cold Water

When it comes to removing caked on oils, greases, and proteins, hot water pressure washers offer a distinct advantage in terms of time, results, and environmental impact. Hot water pressure washers raise the water temperature from about 53°F to as high as 311°F. This allows the working pressure, cleaning time, and consumption of detergent to be greatly reduced.

In addition to these benefits, a significant reduction in germs can be observed when cleaning with hot water. For most hygiene requirements, this germ reduction without the use of disinfectant is fully sufficient. Heat is an important factor in cleaning, as it accelerates various chemical processes. With every 50°F increase in temperature, the chemical reaction speed is doubled. Oil, grease, and soot are dislodged by the heat and easier to remove. The emulsion of oil and grease in water is accelerated and heated surfaces dry faster.

This means that higher water temperatures can reduce cleaning times by up to 35% – with significantly better results. By reducing the water quantity, a steam temperature as high as 311°F can also be achieved. With the combination of mineral-free steam and pressure, even the most difficult dirt can be loosened. This in turn ensures high cleaning performance, even without chemical additives. The steam stage is perfect for removing bitumen coatings, paint coatings in general, soot deposits, lichens and algae.


PSI and GPM are equally important when choosing a pressure washer. PSI refers to the amount of pressure, and GPM refers to the rate of water flow. The correct combination of PSI and GPM in a machine will lead to optimal cleaning results.

To clean effectively, a pressure washer produces a "stripping" action to remove dirt and grime. From here, the "flow" moves the dirt away. Think of the pressure (PSI) as the stripping force that is applied to the surface you are cleaning and the flow (GPM) as the rinsing power.

PSI (Pounds per Square Inch) refers to the amount of cleaning pressure that the unit can produce.

GPM (Gallons per Minute) is the amount of water that is coming from the unit.

Cleaning Units (CU) are the result of multiplying the PSI by the GPM. Cleaning units give the user a measure of unit performance (efficiency) to compare one unit to another.

For example:

  • A pressure washer with 3000 PSI and 2.0 GPM has 6000 Cleaning Units
  • A pressure washer with 2000 PSI and 3.0 GPM also has 6000 Cleaning Units, but the rinsing power is greater than the stripping power.

A general rule is that high PSI pressure washers are better suited for removing oils and caked on materials, while high GPM pressure washers are ideal for removing soil and dirt. Thus, GPM is usually more important to contractors than PSI, as most use cleaning chemicals to do all of the cleaning/lifting of dirt.

Belt Driven vs. Direct Drive

Belt drives are most commonly found on commercial/industrial style pressure washers. A belt driven pump is ideal for cleaning applications that require more than 20+ hours per week. On a belt driven unit, the high-pressure pump spins at a lower RPM, reducing the heat and vibration. This results in minimal wear and tear on the internal parts of the pump and leads to longer life.

If using the pressure washer less than 20 hours a week, a direct drive unit may be the better option. Direct drive units turn about twice the RPM as a belt driven unit, but they are usually more compact and easier to transport.