Medion X20 SW+

Suction in pascal, as the maker measures it. More pascal helps on carpet, but it says little about how well the robot picks grit off a hard floor.

A brush that guides hair to the side instead of letting it wind around the shaft. It saves the cutting work in homes with long hair or pets. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

The side brush swings out in a corner or along a kickboard, so the dust there is swept in too. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

The robot notices when it drives onto a carpet. Most then raise their suction, and a mopping robot lifts its mop or leaves it at the dock.

Whether the robot copes with pet hair: a brush that hair does not wind around and a dock that empties the bin for you. Where the maker does not say so itself, we read it from those two.

The filter the exhaust air passes through. A HEPA filter holds back fine dust and pollen, which counts if someone at home has an allergy.

How the mop is built: flat pads, two spinning discs or a roller. Discs press harder on dried-on dirt, a roller rinses itself while it works.

The pad slides out along a wall or a kickboard, so the last few centimetres are mopped as well. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

The robot leaves the mop at the dock before it vacuums a carpet, so the carpet never gets wet. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

How much clean water the robot carries. It sets how long it mops before a refill, which a dock does by itself.

The dock empties the robot’s dust bin, usually after every run. You only empty the dock’s bag or bin.

The dock collects dust in a bin instead of a disposable bag. No bags to buy, but you empty it yourself.

How much the dust bag in the dock holds.

How the robot maps your home and follows that map. Lidar measures with a laser and works in the dark, a camera looks along and recognises more.

The highest threshold the robot takes, as the maker states it. Measure your own: the step into a bathroom or onto a balcony is often higher.

An extending leg or wheel that carries the robot over a high threshold. Without one it usually stops at about 2 cm. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

How tall the robot is. It decides whether it fits under your sofa, bed or cabinet.

How wide the robot is. Narrower gets between chair legs more easily, wider usually means a bigger dust bin.

What the robot weighs. It counts most if you carry it up a staircase every day.

How much dust the robot holds before you empty it. It matters less with an auto-empty dock, which empties the bin after every run.

The noise in decibels, in the setting its source names: makers mostly give the standard setting, shops often the highest. 65 dB is like a vacuum at half power, 55 dB like a conversation.

The capacity of the battery. It hints at the runtime, but how much the robot draws counts just as much.

How long the robot cleans on one charge, at its quietest setting. After that it recharges and carries on where it stopped.

How long an empty battery takes to charge fully in the dock.

The warranty the maker gives in Germany. Consumer law here stands apart from it and can last longer.