Dreame D20

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: from the maker's product text, not from a specification table.

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.

A sensor notices where more dirt lies, at the doormat for example, and the robot cleans that patch longer or a second time.

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.

How far the robot lifts the mop when it drives onto a carpet. From about 10 mm a medium pile stays dry.

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.

The robot returns to the dock during a run to rinse the mop, instead of pushing dirty water around. 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 collects dust in a bin instead of a disposable bag. No bags to buy, but you empty it yourself. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

The dock mixes detergent into the water itself, from its own bottle. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

The dock can be connected to the tap and the drain, so you never fill or empty a tank. It does need a connection nearby. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

The width, depth and height of the dock. Measure the spot you have in mind, and leave room for the lid and for the robot driving in.

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.

How the robot sees loose things on the floor, such as cables, socks or a pet accident. A camera with depth sensing sees more than a bumper that reacts on contact.

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 while cleaning, 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. Emptying by the dock is louder and listed on its own.

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. On this model: from the maker's product text, not from a specification table.

Matter is the standard that lets devices from different makers work together. With it you can run the robot outside the maker’s own app. On this model: Assumed, not a stated fact: the maker's full specification does not name it, so we take it as no.

Which voice assistants the robot works with, such as Google Assistant or Alexa. On this model: from the maker's product text, not from a specification table.

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