The weight ceiling decides before anything else does

Every automatic unit here publishes a cat weight range, and that range is the first filter, not the last. The spread is wide. The PETKIT PuraMax 2 and CATLINK Scooper Open-X both top out at 22 lbs, the Litter-Robot 4 and PetSafe ScoopFree SmartSpin at 25 lbs, the Litter-Robot 5 Pro at 30 lbs, and the Neakasa M1 at 33 lbs. CatGenie frames its figure differently, stating the most consistent success for up to two cats of up to 20 lbs each, with a third possible depending on behavior and temperament.

None of these manufacturers publishes what the unit does when a cat exceeds the range, so treat the ceiling as a hard limit rather than a suggestion. A 24-lb cat clears four. A 28-lb cat clears two. A cat above 33 lbs clears none, and the manual pan is the only product left.

The low end matters too if there is a kitten in the house. The minimums are in the table, and PetSafe also specifies at least six months old. Whisker states the LR5 Pro’s weight detection works for cats of 3 lbs and up, which is the clearest statement here that per-cat tracking is tied to the sensor range, not just to cycling.

The IRIS manual pan publishes no weight figure because it has nothing to sense. That is the reason to include it: it is the one product in this comparison that a cat of any size can use without a specification check.

Day counts are per cat; divide them

Six units store waste in a bin or drawer, and every one publishes its capacity in liters, which is the unit all of them use in the documents retrieved, along with an emptying estimate, which every brand but PetSafe states for one cat; the comparison table lists all six.

The day counts do not track the liters. PETKIT’s 7 L gets the same 15 days as CATLINK’s 12 L, and Whisker’s smaller liner gets fewer days than either. Each estimate is the manufacturer’s own and they are not made on a common basis, so compare the liter figure first and use the day count only as a sanity check.

Dividing the single-cat estimate by the number of cats is the rough proxy this guide uses. With three cats, both Litter-Robots land at about 3 days or under, and the Neakasa, PETKIT and CATLINK between about 4.5 and 5 days; PetSafe gives no cat count to divide.

Two products sit outside this math. The CatGenie has no bin at all; it flushes solid waste through a drain line each cycle, and its consumable clock is the SaniSolution cartridge instead, 120 cycles on Time or Manual mode and 240 on Cat Activation mode. The IRIS pan has no bin either, because the owner is the mechanism.

Litter capacity is the spec most brands skip

Only three automatic units publish a litter figure, and they do not all publish the same kind. CATLINK states a fill of clumping clay to the MAX line, and Neakasa states roughly 1.8 times that figure; both are in the table. PETKIT publishes 76 L, but that is the interior cylinder’s volume, not a litter fill amount, so it says the drum is large without saying how deep the bed runs. Whisker publishes no reservoir figure for either Litter-Robot, and PetSafe publishes none for the SmartSpin.

For the units with no published figure there is no way to compare refill frequency before buying, and the scores reflect that gap as unverifiable rather than as a judgement about how often you will refill.

The IRIS has no fill line, and the whole basin is open floor rather than a globe or drum.

Entryways: globes publish width, open-tops publish height

Only Whisker publishes both dimensions of its opening: 15.75 x 15.75 in on both Litter-Robots, with a step height of 6.9 in on the LR4 and 7 in on the LR5 Pro, a difference inside rounding. Interior globe height is 16.5 in and 17.5 in respectively.

The open-top units publish the other axis. CATLINK states a 13.8 in (35 cm) entrance height and Neakasa 13.86 in, again near-identical, and neither publishes a width. PETKIT states an approximately 7.87 in threshold without a confirmed width. PetSafe describes a low-profile entry approximately 12 in from the ground and nothing else. CatGenie publishes no entry dimensions at all.

So the question “is the entry too small for my cat” can be checked against a published width only for the two Litter-Robots. For a wide-bodied cat, the open-top units’ height figures tell you how far the cat climbs, not whether it squeezes. Measure the cat, compare it against the one brand that gives you a width, or accept the IRIS’s open top, which has no entry restriction.

Per-cat tracking is not standard equipment

For a multi-cat home, knowing which cat used the box is the feature the app promises and the one most of these units do not actually publish. Whisker is explicit: the LR4 is rated for up to 4 cats and SmartScale tracks individual cat weight; the LR5 Pro is rated for up to 5 cats and adds dual 1080p AI cameras with facial recognition for identification beyond weight. Both include this by default.

The scores treat an unpublished limit as unverifiable rather than as absent, but a buyer who wants per-cat data has two units with a published figure and one with a published add-on.

Count named mechanisms, not adjectives

Every automatic unit here rotates or sifts around a live animal, and “safe” is not a specification. What is checkable is which mechanisms the manufacturer names, and the table’s last column lists them.

Three brands name a gear or rotation design specifically aimed at pinching: CATLINK, PETKIT and Neakasa. PetSafe names exit sensing but no anti-pinch mechanism. The Neakasa figure carries a footnote: the product page gives 5 pairs of infrared sensors for the M1 and 6 sets for the M1 Plus, and which variant the Amazon listing ships was not confirmed.

The CatGenie is a plumbing decision first

The CatGenie A.I. belongs to a different category of commitment. It needs an electrical outlet, a cold-water inlet and a drain hose, and it ships T-adapters for two connection types: 1/2 in OD (3/8 in ID) for a bathroom and 1 in OD (3/4 in ID) for a laundry room. In exchange, nothing is emptied. Solid waste flushes each cycle and the washable granules are reused, with one box lasting about 5-6 months for one cat and CatGenie’s instruction never to load more than one box at a time.

The constraints run the other way too. CatGenie’s stated capacity, up to two cats of up to 20 lbs each, is the lowest stated figure of any kind here, and it publishes no entry dimensions, no per-cat identification and no anti-pinch sensing. A household with a 25-lb cat and perfect plumbing access is still outside what CatGenie describes.

Consumables and connections

Each automatic unit ties you to something. Whisker uses proprietary waste drawer liners on both Litter-Robots and CATLINK uses proprietary waste bags. Neakasa states it uses waste bags without calling them proprietary, and PetSafe and PETKIT state a sealed drawer or bin with no liner requirement in the documents retrieved. CatGenie needs its SaniSolution cartridge and washable granules. The IRIS needs litter.

When the manual box is enough

The IRIS XX-Large is here as the baseline, and for some readers it is the answer. Its case rests on three facts: there is no weight sensor to exceed, no entry to fit through, and no consumable other than litter. A cat above 33 lbs has no automatic option here at all. A cat between 30 and 33 lbs has one.

It is not enough when the frequency math is the reason you are shopping. Scooping daily is the fixed cost of the open pan whatever the cat count, and the IRIS offers no per-cat data, no sealed storage and no sensing.