Water Softener using 150 gallons of water a day to regenerate?
Water softeners do use water to recharge, but it shouldn't be that much. With a new filter and all electronic controls working, most systems should send no more than 25 gallons through during a recharge cycle.

The theory is that the filter media (special polymer beads, often stored in what looks like a high-pressure air tank) is "charged" with a high amount of sodium ions from the rock salt you load into the bin. Hard water containing calcium and magnesium carbonate, which are only slightly soluble and cause lime scale, comes into the filter from the house supply, and the sodium replaces the calcium, forming highly water-soluble sodium carbonate in the water supply, which won't cause scaling, leaving the calcium and magnesium ions in the filter. To "recharge", the softener fills the salt bin with supply water producing a brine, which is then flushed through the filter media. The sodium replaces the calcium and magnesium in the filter, which then hitch a ride down the drain as soluble chlorides.

The amount of water needed to produce the recharging brine varies by manufacturer and age of the filter media; this ion exchange does take its toll, as the charged ions are corrosive (a surplus of positive ions in a water solution makes the solution acidic). The softener also relies on several detectors to determine system status, that are exposed to hundreds of thousands of gallons of water over their rated life, much of it salty and highly corrosive. Over time, all these components wear out, with more or less detrimental effects on the system's overall efficiency.