As compared to a regular hose power washer could use lesser water. This is because the pressure in the water helps to clean off debris and dirt faster. Thus, saving water. There is no fixed amount of water used by the machine. Some washers use a gallon and more per minute whereas others use lesser. This factor depends on each pressure power washer. So, the higher the pressure, the more efficiently will the machine work. Therefore lesser water will be consumed and wasted.