I prefer gas, because they are completely portable. Always use a fan tip regardless of the PSI's you decide upon.
When I use a power washer, I want a 3500 PSI. You can reduce the pressure by backing away from the work area and on stubborn areas, you can come in to the work.
A fan tip is most important.
Then too, the psi requirement has so much to do with the degree of buildup.
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