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What GPM Pressure washer should I buy?

In addition to pressure, GPM is one of the other most important factors to consider when buying a pressure washer.  While we go into great detail on everything you should consider when buying a pressure washer in our complete guide here, this article will specifically cover what to consider about pressure washer GPM when buying a pressure washer.

 Why Pressure Washer GPM matters

The GPM of a pressure washer is one of the biggest factor that determines how fast you will clean a given surface.  Pressure is critical to ensure you can successfully remove what your aiming to from a surface (for more on pressure refer to our guide here) but GPM is the main factor that determines how fast you can clean a set area. 

In addition to cleaning speed, the GPM of your pressure washer will impact  what accessories you can use with your pressure washer.  If you plan on cleaning large flat areas like driveways or decks you may want to consider a surface cleaner, which disperses the pressure washers cleaning power over a wider area so you can get things cleaned much more efficiently.  Surface cleaners come in a variety of diameters with various options of the number of nozzles they have on them.  If you want to run surface cleaners you need a minimum of 3 GPM however the more GPM you have the larger the surface cleaner you can use. 

One other factor to consider is the water supply you will have available.  If you will be using well water as your supply or a portable water tank, you want to ensure you will have the volume of water your power washer will need.  To determine if your water supply will be able to accomodate a certain GPM power washer you can run the hose into a bucket for 1 minute to see how much water is produced.  If you will be using a water tank with your pressure washer, just realize the size of the tank in gallons / GPM will determine how long you will be able to clean before needing to refill your washer tank.

Pressure Washer GPM and Cleaning Efficiency, How they relate

So the two main reasons that GPM matters is how fast you can clean surfaces and the tools you can use with your pressure washer.  In general the more GPM you can purchase the more cleaning efficiency you will achieve and the greater flexibility you will have when it comes to surface cleaners.  The chart below shows the efficiency of various pressure washers to show you the cleaning speed improvements of different GPM washers (assuming the pressure of the washer stays the same).  The basic way this chart is figured out is based on the cleaning units of the pressure washer.  Cleaning units are calculated using pressure x GPM.  A higher cleaning unit measurement will enable faster cleaning speeds.  The difference between two pressure washers cleaning units will determine the approximate time savings. For example, take a surface that takes 14 minutes to clean with a 2 GPM pressure washer at 3000 PSI.  If we purchase a 3 GPM pressure washer at 3000 PSI that gives us an additional 3000 cleaning units which is equivalent to approximately a 50 percent increase in performance (3000/ the 6000 units from the original washer) that results in a 50 percent decrease in processing time.    This math and the chart below can help you better understand the benefit your getting from considering a higher vs lower GPM pressure washer.


Cleaning Time*


2.5 GPM


3.5 GPM


20 min

18 min

16 min

14 min


12 min

10 min


8 min


6 min


4 min


2 min

*Times shown are for comparison use only. Actual times will depend on operator skills and condition and size of job application.


Final thoughts around GPM and pressure washers

To simplify choosing a pressure washer with the right PSI and GPM you can take the following two steps:  Ensure you choose a pressure washer with enough Pressure to meet the minimum pressure requirements for effective cleaning of your surface, you can refer to our guide here for help with PSI and pressure washers. Once you have confirmed a pressure that will work for your needs, choose a GPM knowing 3 GPM will give you the ability to use a surface cleaner and higher GPM output will provide faster cleaning times.  For more you can check out complete buying guide out on pressure washers. 

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