Robot vacuums: what they genuinely replace

A robot will not replace your vacuum cleaner. It replaces the daily tidy-up, which is a different job and arguably a better one to automate.

What it is actually good at

Suction on a robot is a fraction of an upright's, and no amount of specification-sheet Pascals changes that. What a robot has instead is frequency. Running every day on a floor that would otherwise be done weekly, it removes dust before it is trodden in.

The net result on hard floors and low-pile carpet is usually cleaner than weekly deep-vacuuming, even though any single pass is weaker.

Where it struggles

• Deep or shaggy pile. The brush bar cannot reach the base of the fibre. Thick rugs get skimmed, not cleaned.
• Corners and edges. A round body cannot reach a right angle. Side brushes help; they do not solve it.
• Clutter. Cables, socks and chair legs stop a run. Ten minutes of tidying beforehand is the price of admission.
• Stairs. Obviously — but people still forget when budgeting for one.

Navigation is what you are paying for

The single biggest quality difference between a cheap unit and a good one is not suction. It is how it decides where to go.

Random-bounce models wander until the battery runs down. They eventually cover a room, wastefully. Mapping models — lidar or camera — drive in orderly lines, know which rooms they have finished, and resume where they stopped after charging. On anything larger than a flat, that difference is the whole experience.

The bin is the real constraint

A robot's dust bin holds a fraction of a litre. On a shedding carpet or with a pet in the house, that is one or two runs before it stops picking anything up. Emptying it is a daily job unless you buy a model with a self-emptying base, which is what most of the price difference at the top end actually buys.

Getting a useful result

• Run it daily, not weekly. Frequency is the entire point.
• Give it a tidy floor. Treat it as a reason to keep cables off the ground.
• Clean the brush bar weekly — hair wraps around it and quietly kills performance.
• Keep a proper vacuum for edges, stairs and the monthly thorough job. The robot is a supplement, not a replacement.