The N+1 rule bends for automation but does not vanish. One machine covers capacity, never location. Here is what five years with three cats taught me.
Do You Need a Second Automatic Litter Box?
The trigger is behavior, not drawer volume. And the second box does not have to be automatic, a plain pan provides a location just as well.
Self-Cleaning Litter Box Cost vs Manual: The Real Math
The honest comparison is a worksheet, not a total. Here are the five cost lines that decide it, and the one variable that swings it most.