This depends on the type and size softener you have. Basically the softeners are broken into 2 types, day and metered. A Day Type is set to regenerate, as the name suggests, every so many days, typically every 3 to 4 days. This will occur no matter how much water you use. Even if you go away and use no water, the unit regenerates and uses salt and electricity, for your pumps and causes unnecessary wear and tear on your equipment. The Metered Type is set at a predetermined number of gallons, based on the size of the unit and the hardness of the water, which is obtained by a hardness test. If no water is used, the meter does not count down and delays the regeneration, thus saving on salt, electricity, and wear and tear on pumps. Besides the differences mentioned above, there are also choices to be made as to size of the softener tank, and between digital or mechanical valves. Again, these decisions are based on budget, water use, and water conditions. Another factor that influences the amount of salt that you use is the hardness of your water. The more hardness in your water, the more salt is required to soften the water.