I have a Gerni which is at the bottom of their range, so it's not the most powerful, but is plenty powerful enough to do the job. I chose Gerni because you could get two nozzles for it specifically for cars. One is a right angle so you can do the underneath easily, the other is a car nozzle supposedly producing a more gentle spray than the regular one. If you want to use snow foam, the plastic bottle these washers come with doesn't work, I tried it. You need a specific foam lance that clips on to the end of the wand. I got the Autobrite one, it works really well. It comes in different fittings to suit the brand of washer you have. I also use the Autobrite MagicFoam, also seems very good, although doesn't smell that good!