Litter-Robot 4 vs 5: Which One Should You Buy?

What actually changed — and what didn’t

Strip away the launch copy and the 5 differs from the 4 in two clusters: sensing and fit.

On sensing, the 5 adds WasteID — it distinguishes urine from feces per visit, an industry first. Whisker says the machine uses it to time its cycles: it waits longer after urine so clumps can form, and cycles quickly after solid waste to contain odor. Paired with the built-in SmartScale (every visit is weighed, per cat), the litter box becomes an early-warning system — a cat that suddenly urinates more often is a classic early kidney and diabetes flag, and the 5 can surface that per cat without any extra hardware. The 4 tracks visits and weights through its app too, but with no urine/feces distinction and a scale that tops out at 25 pounds.

On fit, the 5 raises the rated cat weight from 3–25 lb to 3–30 lb, the capacity rating from 4 cats to 5, stretches the waste drawer from roughly 8 days to 10 between empties for one cat, adds about an inch of interior headroom, and ships with a base that runs correctly on carpet — the 4 needs a separate carpet-tray accessory for that. There’s also a full-color LCD on the base (the 4 has an indicator-light bar), an appliance-grade ABS finish, easier access to the curtain-sensor lens for cleaning, and a bonnet that’s ready for Whisker’s LitterHopper automatic litter refill.

What didn’t change matters just as much. The footprint is essentially identical — 22" wide, 27" deep, 29.9" tall against the 4’s 29.5" — so neither machine squeezes into a spot the other can’t. The step height is within a tenth of an inch. Both carry the same 90-day trial and 1-year warranty on direct orders. And the core mechanism — a rotating globe that sifts clumps into a sealed drawer a few minutes after every visit — is the same idea, executed well, on both.

The case for the Litter-Robot 4: proven, cheaper, fixable

The 4 has been Whisker’s volume seller since 2022, and that maturity is worth real money in this category:

• The firmware is settled. Years of updates have worked through the sensor quirks that every new robot litter box launches with — exactly the phase the 5 is in right now.
• The parts and repair ecosystem is the biggest in the category. Motors, sensors, boards, globes — all available, with years of community repair knowledge behind them. Our own Litter-Robot 3 was still getting supported parts five years in, and the 4’s ecosystem is larger still. A machine you’ll own for five-plus years should be judged on how fixable it is in year four.
• It actually goes on sale. The 5 is too new to discount; the 4 shows up on deal trackers regularly — bundles have been listed in the $560–650 range in recent months, and Whisker sells reconditioned units for less again. Prices move, so treat those as patterns rather than promises, but the practical gap between a discounted 4 and a full-price 5 is often a lot more than $100.
• For a one- or two-cat home on hard floors, it gives up nothing that matters day to day. The always-clean core job is identical. Our full LR4 verdict is here.

The case for the Litter-Robot 5: four homes where it wins outright

The 5’s upgrades aren’t spread evenly across all buyers — they concentrate on four specific profiles, and if you’re in one of them the comparison stops being close:

1. Your cat is over 25 pounds. The 5 (and 5 Pro) are the only rotating units rated to 30 lb. For Maine Coon owners this is the whole decision — the 4 is simply not rated for your cat.
2. You run three or more cats. The 5-cat rating, the ~10-day drawer, and per-cat WasteID tracking all compound in a multi-cat home. Scaled down, a three-cat home empties the 5’s drawer roughly every three days — with the 4 you’re closer to every two.
3. The machine is going on carpet. The 5 handles it as shipped; the 4 wants its add-on tray to run reliably. One less accessory, one less failure mode.
4. You want health telemetry without extra hardware. WasteID plus the 30 lb SmartScale is genuinely new — no other machine tells you *which* cat urinated and how often. If you’ve ever had a cat with kidney disease or diabetes, you know why catching that trend a month early matters.

One compatibility note that applies to both machines but bites harder on the sensor-rich 5: these are designed for clumping clay litter. Owner reports are consistent that alternatives — tofu pellets especially — confuse the sensors. A household committed to non-clay litter should be looking at a different category entirely.

Already own a 4? The upgrade math says wait

This is the question most people searching "Litter-Robot 4 vs 5" are actually asking, so here it is plainly: a working Litter-Robot 4 is not $799 worse than a Litter-Robot 5.

Early hands-on reviews of the 5 tell a consistent story — strong hardware, immature software. Reported issues include inconsistent waste measurements, cat-detection sensor errors, drawer-level warnings firing early or late, Wi-Fi and Bluetooth drops, and some settings living only in the app rather than on that new LCD. Cats.com scored the 5 a 4.6/5 and still explicitly advised LR4 owners to wait for firmware fixes; BGR’s verdict on the 5 Pro was blunter — fancy features, too many bugs. None of this is unusual for first-year firmware on new hardware, and Whisker’s update track record is decent. But paying $799 to beta-test replaces a machine that already works.

The sensible upgrade triggers are the same four profiles above — your household changed (a new cat, a move to carpet, a cat outgrowing the 4’s ratings), or your 4 is aging out of its service life anyway. Absent one of those, the move that actually improves your setup this year costs $0: keep the 4, let the 5’s firmware mature, and revisit when your 4 needs replacing — by which point the 5 will be cheaper, patched, and possibly superseded.

What five years on a Litter-Robot 3 taught us about this choice

Our own unit is a refurbished Litter-Robot 3 that has cycled daily for about five years — the full long-term review is here. Two lessons transfer directly.

The platform outlives the spec sheet. Our 3 was secondhand when we got it and still runs. Whatever you pay up front spreads across a service life measured in years, which is why we weight firmware maturity and parts availability so heavily in this comparison — they’re what year four looks like.

Acceptance is per-cat and binary. The same machine in the same house got a permanent yes from one of our cats and a permanent no from the other. No feature on either spec sheet changes that: some cats will not use a moving litter box, full stop. That’s why the 90-day in-home trial Whisker advertises on direct orders matters more than any row in our table, and why you should keep a regular box running through the transition — whichever machine you pick.

Related reading

• Litter-Robot 3, five years in: a long-term owner review — the first-hand experience behind this site’s take on the category
• Litter-Robot 4: is it actually worth $700? — the default pick, judged on its own
• Litter-Robot 5: is the $799 upgrade actually worth it? — the deeper dive on the new flagship, including the 5 Pro
• Litter-Robot 4 vs PETKIT PuraMax 2 — if the budget question comes first
• Are automatic litter boxes worth it at all? — with a cost calculator to run your own numbers