PSI vs GPM: What Matters Most?

Imagine PSI being a “stripping” action to blast off the grime with force on the surface you’re cleaning and GPM as the “flow” to move/rinse the dirt and grime off the surface.

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

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

SIMPSON measures this PSI/GPM combination to create Cleaning Units (CU.)

Cleaning Units (CU) is the result of multiplying the PSI by the GPM. Cleaning units gives us a measurement of machine performance (efficiency) to compare one pressure washer to another.

Example:

Pressure washer A has 3000 PSI and 2.0 GPM = 6000 Cleaning Units

Pressure washer B has 2000 PSI and 3.0 GPM = 6000 Cleaning Units

The difference? The rinsing power is greater in pressure washer B than the stripping power. Meaning, Pressure washer B will clean (rinse dirt away) faster than pressure washer A.  Although the CU is the same in both pressure washers, the higher the GPM, the faster the job will be finished.

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