Knowing the right amount of power to look for is crucial when you’re in the market for the perfect pressure washer. It also determines whether an electric unit will suffice or if you should upgrade to a gas-powered one. But when it comes to the pressure washer PSI vs. GPM discussion, which factor holds more significance?
Understanding PSI and Its Impact
PSI, or pounds per square inch, is a measurement that most people associate with pressure washers. It represents the force of the water’s impact and helps determine its ability to dislodge stubborn debris. A higher PSI generally means more energy in the water, making it more effective in many cases. However, excessive pressure can be detrimental. Even with a moderately powerful and narrow nozzle, you run the risk of inadvertently stripping paint off vehicles or damaging wooden decks. By using the widest possible nozzle angle, you can control the water’s impact while still achieving the desired level of cleaning.
The Role of GPM in Pressure Washers
GPM, short for “gallons per minute,” measures the water flow rate from a pressure washer. It determines how effectively you can wash away the dirt and grime. Unlike PSI, there isn’t much risk of damage associated with the water’s flow rate. A higher GPM rating means you can cover larger areas more quickly once the pressure has loosened the dirt.
The Winning Combination: PSI vs. GPM
In reality, it’s the combination of PSI and GPM that achieves optimal results. The winner between PSI and GPM depends on the specific task at hand. Are you frequently tackling the challenge of removing chewing gum from sidewalks or dealing with stubborn tar stains? In that case, a higher PSI rating would be more beneficial. On the other hand, if you’re primarily engaged in standard household cleaning tasks such as washing sidings, windows, and decks, a higher GPM rating would allow you to work more efficiently.
The Key to Making the Right Choice
For most homeowners, it’s recommended to start with determining the ideal PSI level. Once you’ve established the desired PSI, focus on finding a pressure washer with a higher GPM rating for better efficiency. In situations where you’re comparing two or more pressure washers with similar PSI ranges, consider the cleaning unit formula. By multiplying the PSI and GPM values, you can get an estimate of the total cleaning potential.
Let’s take a look at a couple of pressure washers from the Simpson MegaShot line as an example:
| MegaShot MSH3125-S | MegaShot MS60921 | |
|---|---|---|
| PSI Rating | 3200 psi | 3300 psi |
| Gross Margin Rating | 2.5 gallons | 2.4 Gross profit margin |
| Cleaning Unit (CU) | 3200 x 2.5 = 8000 cubic meters | 3300 x 2.4 = 7920 cubic meters |
Although the MS60921 has a higher PSI, the MSH3125-S actually has a higher cleaning unit. While they are close in performance, in this case, the lower PSI machine can accomplish the job more efficiently.
The Bottom Line
The best pressure washers strike a balance between PSI and GPM through the intentional pairing of the motor and pump. Typically, as you increase the PSI, the GPM also increases. Remember the cleaning unit formula when comparing different models as you shop.
If you’re still unsure about the ideal combination, we recommend starting with a pressure washer that falls within the 3000 – 3500 PSI/2.0 – 2.5 GPM range. These pressure washers are generally suitable for most homeowners as they offer efficient performance while remaining affordable. To speed up the cleaning process for driveways, decks, and walkways, consider using a surface cleaner alongside your pressure washer.
In this article, we highlighted the Simpson MegaShot MSH3125-S and the Simpson MegaShot MS60921 models, both available for around $400 at The Home Depot and Tractor Supply, respectively. To see how the Simpsons fared, check out our MS60921 review.