The $100 Sun Joe washers at Sam's club have done very well for washing my cars and Grandson's vehicles. Seem to have enough pressure to do the job and no danger of removing paint.
120V plug in beats fighting with a gas motor. The farm also has a Honda powered, CAT pump variety but it's overkill for car washing. TBH, I've got more money tied up in extended hoses, improved hand gun, foam canon, & etcetera but the little Son Joe is at the heart of it all and it continues to keep some of my neighbors entertained by me always having a clean car.