There is no universal gallons-per-cycle number. Larger resin beds and inefficient settings use more water, while demand-initiated controls reduce unnecessary regeneration frequency.
Why regeneration uses water
Backwash lifts and cleans the resin bed, brine regenerates exchange sites, and rinse cycles remove residual salt before the unit returns to service.
Bigger systems use more per cycle but may regenerate less often
A larger resin bed can require more regeneration water per event but provide more capacity between events. Annual water use is therefore more useful than judging one cycle.
Sizing matters
An undersized unit can regenerate frequently; an oversized unit can cost more upfront and create other inefficiencies. Size to measured hardness and realistic household flow.
Salt-free systems avoid regeneration
Salt-free conditioners do not regenerate with brine, but they also do not remove hardness ions like a true softener.