Quick answer: For multiple cats, look for an automatic litter box with a large interior, fast cycle time, high-capacity waste drawer, and sensors that handle frequent back-to-back use without jamming.
Most automatic litter boxes are designed for average-sized cats. In a multi-cat household you likely have cats of different sizes. Look for models with the largest available opening and interior — cramped boxes are avoided by larger or older cats, defeating the purpose.
Some models require a minimum wait time between cycles (3-10 minutes) to let litter settle. In a busy household, cycles need to run frequently. Look for adjustable wait times and a waste drawer large enough to handle multiple uses before emptying.
The standard rule is one litter box per cat plus one extra. For two cats, that means three boxes ideally — not one automatic box for both. An automatic box reduces daily maintenance significantly but doesn't replace the per-cat box ratio needed for harmonious multi-cat households.
An automatic litter box in a multi-cat home works best as a supplement to your full box count, not a replacement. Size and cycle frequency are the most important specs.