EZIclean I-Bot Z5

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 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 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.

Sensors under the robot that see a drop, so it stops at the top of a staircase instead of falling down it.

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

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.

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.

Which voice assistants the robot works with, such as Google Assistant or Alexa.

You set days and times, and the robot starts by itself, also when you are not at home.