Its a common mistake to think of pressure as the more important decision when getting a pressure washer. It's the GPM that is really the most important with pressure washers. Its a trade off with a given HP. Put simply, I'd rather have a 1500 to 2000PSI machine at 3 gpm then a 2500 to 3000 PSI machine at 2 gpm. I have a little electric pressure washer that has plenty of pressure but very little volume. I also have a gas at 3500 PSI and 4 gpm. I can easily use the larger washer on my tractor, leaving the decals, paint etc. fine if I'm using the wider angle tip (usually white colored). When it comes to pressure washers that most folks get at places like Home Depot, your decision about pressure is very limited based on price. 5 to 6 HP, $600, will get you around 2.5 gpm and 2000 PSI. Always opt for the higher GPM when you can. Wheter its 1500 PSI, 2000 PSI or higher, you will find all do a pretty good job. If you want to really see how volume affects the time and practicality it takes to wash down something, try using a airless paint sprayer. Basically a pressure washer with high pressure, 3000 PSI and up but very low GPM, typically well under 1 GPM. It would take some time even if the proper tip could be had. Rat...