I have a Nilfisk E130 and its been fantastic. Paid ~200 a few years ago. Wash 3 cars with it weekly and do my drive way, bricks and pavements twice a year not to mention all the other uses. Just do not leave it outside to freeze and try using it!
Yeah put it in neat, the lance will mix it with water. Depending on the lance it might have an adjustment to control the concentration.