Ecovacs Deebot N20 Pro+

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.

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.

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.

The dock dries the mop afterwards, so it does not sit there wet and start to smell.

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.

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

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 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.