Not much. Soft washing systems are equipped with power washers and cleaning agents. They are the same as the traditional pressure washing method. The only difference is soft washing systems use solution tanks to hold the cleaning agents. Soft washing systems are selling gimmicks, and the customer should be aware. Power washers contain a detergent ejection system that allows the right combination of water and detergent to pass through the pump. It does the same thing as solution tanks. The only way to successfully clean vinyl siding is to use low pressure, cleaning agents, and soft bristle brushes to scrub the vinyl siding. Soft washing systems are a near worthless method.