How big a hopper do I actually need?

A r/izreview comment widely echoed in the threads we read makes the point bluntly: a 7L hopper that sits full for three weeks delivers staler kibble than a 4L hopper refilled every five days. For a single cat, 3–4L is generally sufficient; multi-cat homes or large dogs benefit from 5–14L with airtight seals and desiccant packs.