I agree. The gas washers have some serious pressure. Mine works great on the house, driveway, sidewalks, etc. I've had it for a number of years.
After searching the net, it appears that the cold water pressure washer idea is not such a good one for vehicles (other than spraying off some dust). I know car washes use hot water here in the soap cycle and I'm quite sure those cheap bastards would bypass that step if it was not an integral part of the cleaning process. A professional heated water pressure washer is not something I intend to buy, store, and maintain!
Oh well...