The first question you should ask yourself is where you intend to use the pressure washer—at home or at work. A pressure washer used primarily at home probably doesn’t need to be as powerful as one that is used on a job site. Around the house, for example, you shouldn’t need more than 3000 PSI. To be fully productive on the job site, though, you probably need at least 3000 PSI.

Next, ask what you want to clean. If you’re looking to simply take the dirt and grime off the driveway or patio furniture, you can use a unit with relatively low pressure—perhaps 2500 PSI. If, however, you plan on scrubbing mold and mildew off the concrete, or prepping a house for painting, you should consider a unit with a higher pressure.

Finally, think about how much cleaning you will be doing. If you’re cleaning a number of items, or if you need to clean a large area, you might want to consider a unit with a higher GPM. More water means more cleaning power and a higher GPM will make the job go faster.