It is hard to give a dollar amount that will occur on your bill every month, but yes water softeners do use water to backwash the softening resin, however, some units use more than others. There are basically two types of softeners.One is called a day wheel type and regenerates every so many days, based on how often it is set to regenerate. This number is obtained by the professional that installs and/or sells the equipment. He bases the number of days between regeneration on the number of people in the house, the hardness of the water, and the size of the unit. Contrary to popular belief, a larger unit in the long run does not use more salt because it regenerates less frequently than an undersized unit.The second type of softener is called a metered type of softener. This type regenerates based on a preset number of gallons. Again this number of gallons between regenerations is based on a water test preformed by your water treatment professional and takes into consideration the size of the unit, the number of people, and the hardness in the water. The advantage of a metered system is that if you use less water than normal on any given day, the unit foregoes the scheduled regeneration, thus saving on salt and water. Many units also have other economical properties built into their valves, such as a memory that knows what days are typically heavy water days and which are not, and the unit acts accordingly. Aqua Care has a number of options available for you to consider. Just call for a free water evaluation.