The small electric power washer I bought is a BlackMax/Briggs and Stratton 1800 PSI.... comes with a 25' flexible hose and various nozzle attachments to control spray power. I got mine from Sam's Club.
It will get mold off of sidewalks with the smallest concentrated spray dispersion attachment, but takes a little more time, depending on the surface (rough or smooth) and amount of mold buildup. It can, however, cause the wood to fray/splinter if you're not careful. I've never had to use detergent.
So if a smaller electric 1800 PSI unit can cause damage to wood - obviously the bigger units can. Sounds like you're looking for something a little bigger with a little more power, and for that reason I'm not sure you'd be satisfied with the one I bought.
Although I love mine, the purpose it serves for me might not be the same for you, as I'm basically using it for light-duty mold removal off of wood and siding.
I wouldn't ever use it to wash a vehicle though.