For years, I have been using a 25 degree green nozzle to pressure wash my driveway. It too 20 minutes to complete each 150 sq ft square of concrete. After using this surface cleaner, the same area now takes only 5 minutes! And less water! I find that the surface is not quite as deeply cleaned, but my gosh, it is close enough where the time/money savings is worth the slight decrease. I also found that the dirt and water stays under the cleaner, so that I have to hose down the area just cleaned to wash it away. Again, a trade off well worth it. Why did it take me so long to purchase this item??